diff --git a/models/fixtures/pull_request.yml b/models/fixtures/pull_request.yml
index d45baa711c6e7..165437f0328dd 100644
--- a/models/fixtures/pull_request.yml
+++ b/models/fixtures/pull_request.yml
@@ -60,8 +60,8 @@
   head_repo_id: 1
   base_repo_id: 1
   head_branch: pr-to-update
-  base_branch: branch1
-  merge_base: 1234567890abcdef
+  base_branch: branch2
+  merge_base: 985f0301dba5e7b34be866819cd15ad3d8f508ee
   has_merged: false
 
 -
diff --git a/modules/convert/convert.go b/modules/convert/convert.go
index c62b4303ed276..0e67563077131 100644
--- a/modules/convert/convert.go
+++ b/modules/convert/convert.go
@@ -27,6 +27,7 @@ import (
 	"code.gitea.io/gitea/modules/log"
 	api "code.gitea.io/gitea/modules/structs"
 	"code.gitea.io/gitea/modules/util"
+	"code.gitea.io/gitea/services/gitdiff"
 	webhook_service "code.gitea.io/gitea/services/webhook"
 )
 
@@ -414,3 +415,36 @@ func ToLFSLock(l *git_model.LFSLock) *api.LFSLock {
 		},
 	}
 }
+
+// ToChangedFile convert a gitdiff.DiffFile to api.ChangedFile
+func ToChangedFile(f *gitdiff.DiffFile, repo *repo_model.Repository, commit string) *api.ChangedFile {
+	status := "changed"
+	if f.IsDeleted {
+		status = "deleted"
+	} else if f.IsCreated {
+		status = "added"
+	} else if f.IsRenamed && f.Type == gitdiff.DiffFileCopy {
+		status = "copied"
+	} else if f.IsRenamed && f.Type == gitdiff.DiffFileRename {
+		status = "renamed"
+	} else if f.Addition == 0 && f.Deletion == 0 {
+		status = "unchanged"
+	}
+
+	file := &api.ChangedFile{
+		Filename:    f.GetDiffFileName(),
+		Status:      status,
+		Additions:   f.Addition,
+		Deletions:   f.Deletion,
+		Changes:     f.Addition + f.Deletion,
+		HTMLURL:     fmt.Sprint(repo.HTMLURL(), "/src/commit/", commit, "/", util.PathEscapeSegments(f.GetDiffFileName())),
+		ContentsURL: fmt.Sprint(repo.APIURL(), "/contents/", util.PathEscapeSegments(f.GetDiffFileName()), "?ref=", commit),
+		RawURL:      fmt.Sprint(repo.HTMLURL(), "/raw/commit/", commit, "/", util.PathEscapeSegments(f.GetDiffFileName())),
+	}
+
+	if status == "rename" {
+		file.PreviousFilename = f.OldName
+	}
+
+	return file
+}
diff --git a/modules/structs/pull.go b/modules/structs/pull.go
index b63b3edfd30a4..f627241b26307 100644
--- a/modules/structs/pull.go
+++ b/modules/structs/pull.go
@@ -95,3 +95,16 @@ type EditPullRequestOption struct {
 	RemoveDeadline      *bool      `json:"unset_due_date"`
 	AllowMaintainerEdit *bool      `json:"allow_maintainer_edit"`
 }
+
+// ChangedFile store information about files affected by the pull request
+type ChangedFile struct {
+	Filename         string `json:"filename"`
+	PreviousFilename string `json:"previous_filename,omitempty"`
+	Status           string `json:"status"`
+	Additions        int    `json:"additions"`
+	Deletions        int    `json:"deletions"`
+	Changes          int    `json:"changes"`
+	HTMLURL          string `json:"html_url,omitempty"`
+	ContentsURL      string `json:"contents_url,omitempty"`
+	RawURL           string `json:"raw_url,omitempty"`
+}
diff --git a/routers/api/v1/api.go b/routers/api/v1/api.go
index 6a98121b73a51..0d11674aa9971 100644
--- a/routers/api/v1/api.go
+++ b/routers/api/v1/api.go
@@ -1002,6 +1002,7 @@ func Routes(ctx gocontext.Context) *web.Route {
 						m.Get(".{diffType:diff|patch}", repo.DownloadPullDiffOrPatch)
 						m.Post("/update", reqToken(), repo.UpdatePullRequest)
 						m.Get("/commits", repo.GetPullRequestCommits)
+						m.Get("/files", repo.GetPullRequestFiles)
 						m.Combo("/merge").Get(repo.IsPullRequestMerged).
 							Post(reqToken(), mustNotBeArchived, bind(forms.MergePullRequestForm{}), repo.MergePullRequest).
 							Delete(reqToken(), mustNotBeArchived, repo.CancelScheduledAutoMerge)
diff --git a/routers/api/v1/repo/pull.go b/routers/api/v1/repo/pull.go
index dda05203df85a..2cf30e7c47b82 100644
--- a/routers/api/v1/repo/pull.go
+++ b/routers/api/v1/repo/pull.go
@@ -26,6 +26,7 @@ import (
 	"code.gitea.io/gitea/modules/git"
 	"code.gitea.io/gitea/modules/log"
 	"code.gitea.io/gitea/modules/notification"
+	"code.gitea.io/gitea/modules/setting"
 	api "code.gitea.io/gitea/modules/structs"
 	"code.gitea.io/gitea/modules/timeutil"
 	"code.gitea.io/gitea/modules/web"
@@ -33,6 +34,7 @@ import (
 	asymkey_service "code.gitea.io/gitea/services/asymkey"
 	"code.gitea.io/gitea/services/automerge"
 	"code.gitea.io/gitea/services/forms"
+	"code.gitea.io/gitea/services/gitdiff"
 	issue_service "code.gitea.io/gitea/services/issue"
 	pull_service "code.gitea.io/gitea/services/pull"
 	repo_service "code.gitea.io/gitea/services/repository"
@@ -1323,3 +1325,137 @@ func GetPullRequestCommits(ctx *context.APIContext) {
 
 	ctx.JSON(http.StatusOK, &apiCommits)
 }
+
+// GetPullRequestFiles gets all changed files associated with a given PR
+func GetPullRequestFiles(ctx *context.APIContext) {
+	// swagger:operation GET /repos/{owner}/{repo}/pulls/{index}/files repository repoGetPullRequestFiles
+	// ---
+	// summary: Get changed files for a pull request
+	// produces:
+	// - application/json
+	// parameters:
+	// - name: owner
+	//   in: path
+	//   description: owner of the repo
+	//   type: string
+	//   required: true
+	// - name: repo
+	//   in: path
+	//   description: name of the repo
+	//   type: string
+	//   required: true
+	// - name: index
+	//   in: path
+	//   description: index of the pull request to get
+	//   type: integer
+	//   format: int64
+	//   required: true
+	// - name: skip-to
+	//   in: query
+	//   description: skip to given file
+	//   type: string
+	// - name: whitespace
+	//   in: query
+	//   description: whitespace behavior
+	//   type: string
+	//   enum: [ignore-all, ignore-change, ignore-eol, show-all]
+	// - name: page
+	//   in: query
+	//   description: page number of results to return (1-based)
+	//   type: integer
+	// - name: limit
+	//   in: query
+	//   description: page size of results
+	//   type: integer
+	// responses:
+	//   "200":
+	//     "$ref": "#/responses/ChangedFileList"
+	//   "404":
+	//     "$ref": "#/responses/notFound"
+
+	pr, err := issues_model.GetPullRequestByIndex(ctx, ctx.Repo.Repository.ID, ctx.ParamsInt64(":index"))
+	if err != nil {
+		if issues_model.IsErrPullRequestNotExist(err) {
+			ctx.NotFound()
+		} else {
+			ctx.Error(http.StatusInternalServerError, "GetPullRequestByIndex", err)
+		}
+		return
+	}
+
+	if err := pr.LoadBaseRepo(); err != nil {
+		ctx.InternalServerError(err)
+		return
+	}
+
+	if err := pr.LoadHeadRepo(); err != nil {
+		ctx.InternalServerError(err)
+		return
+	}
+
+	baseGitRepo := ctx.Repo.GitRepo
+
+	var prInfo *git.CompareInfo
+	if pr.HasMerged {
+		prInfo, err = baseGitRepo.GetCompareInfo(pr.BaseRepo.RepoPath(), pr.MergeBase, pr.GetGitRefName(), true, false)
+	} else {
+		prInfo, err = baseGitRepo.GetCompareInfo(pr.BaseRepo.RepoPath(), pr.BaseBranch, pr.GetGitRefName(), true, false)
+	}
+	if err != nil {
+		ctx.ServerError("GetCompareInfo", err)
+		return
+	}
+
+	headCommitID, err := baseGitRepo.GetRefCommitID(pr.GetGitRefName())
+	if err != nil {
+		ctx.ServerError("GetRefCommitID", err)
+		return
+	}
+
+	startCommitID := prInfo.MergeBase
+	endCommitID := headCommitID
+
+	maxLines, maxFiles := setting.Git.MaxGitDiffLines, setting.Git.MaxGitDiffFiles
+
+	diff, err := gitdiff.GetDiff(baseGitRepo,
+		&gitdiff.DiffOptions{
+			BeforeCommitID:     startCommitID,
+			AfterCommitID:      endCommitID,
+			SkipTo:             ctx.FormString("skip-to"),
+			MaxLines:           maxLines,
+			MaxLineCharacters:  setting.Git.MaxGitDiffLineCharacters,
+			MaxFiles:           maxFiles,
+			WhitespaceBehavior: gitdiff.GetWhitespaceFlag(ctx.FormString("whitespace")),
+		})
+	if err != nil {
+		ctx.ServerError("GetDiff", err)
+		return
+	}
+
+	listOptions := utils.GetListOptions(ctx)
+
+	totalNumberOfFiles := diff.NumFiles
+	totalNumberOfPages := int(math.Ceil(float64(totalNumberOfFiles) / float64(listOptions.PageSize)))
+
+	start, end := listOptions.GetStartEnd()
+
+	if end > totalNumberOfFiles {
+		end = totalNumberOfFiles
+	}
+
+	apiFiles := make([]*api.ChangedFile, 0, end-start)
+	for i := start; i < end; i++ {
+		apiFiles = append(apiFiles, convert.ToChangedFile(diff.Files[i], pr.HeadRepo, endCommitID))
+	}
+
+	ctx.SetLinkHeader(totalNumberOfFiles, listOptions.PageSize)
+	ctx.SetTotalCountHeader(int64(totalNumberOfFiles))
+
+	ctx.RespHeader().Set("X-Page", strconv.Itoa(listOptions.Page))
+	ctx.RespHeader().Set("X-PerPage", strconv.Itoa(listOptions.PageSize))
+	ctx.RespHeader().Set("X-PageCount", strconv.Itoa(totalNumberOfPages))
+	ctx.RespHeader().Set("X-HasMore", strconv.FormatBool(listOptions.Page < totalNumberOfPages))
+	ctx.AppendAccessControlExposeHeaders("X-Page", "X-PerPage", "X-PageCount", "X-HasMore")
+
+	ctx.JSON(http.StatusOK, &apiFiles)
+}
diff --git a/routers/api/v1/swagger/repo.go b/routers/api/v1/swagger/repo.go
index 3522e242764ee..642b1b7b91023 100644
--- a/routers/api/v1/swagger/repo.go
+++ b/routers/api/v1/swagger/repo.go
@@ -254,6 +254,28 @@ type swaggerCommitList struct {
 	Body []api.Commit `json:"body"`
 }
 
+// ChangedFileList
+// swagger:response ChangedFileList
+type swaggerChangedFileList struct {
+	// The current page
+	Page int `json:"X-Page"`
+
+	// Commits per page
+	PerPage int `json:"X-PerPage"`
+
+	// Total commit count
+	Total int `json:"X-Total"`
+
+	// Total number of pages
+	PageCount int `json:"X-PageCount"`
+
+	// True if there is another page
+	HasMore bool `json:"X-HasMore"`
+
+	// in: body
+	Body []api.ChangedFile `json:"body"`
+}
+
 // Note
 // swagger:response Note
 type swaggerNote struct {
diff --git a/templates/swagger/v1_json.tmpl b/templates/swagger/v1_json.tmpl
index 47100450f945a..52553e2e89919 100644
--- a/templates/swagger/v1_json.tmpl
+++ b/templates/swagger/v1_json.tmpl
@@ -8019,6 +8019,80 @@
         }
       }
     },
+    "/repos/{owner}/{repo}/pulls/{index}/files": {
+      "get": {
+        "produces": [
+          "application/json"
+        ],
+        "tags": [
+          "repository"
+        ],
+        "summary": "Get changed files for a pull request",
+        "operationId": "repoGetPullRequestFiles",
+        "parameters": [
+          {
+            "type": "string",
+            "description": "owner of the repo",
+            "name": "owner",
+            "in": "path",
+            "required": true
+          },
+          {
+            "type": "string",
+            "description": "name of the repo",
+            "name": "repo",
+            "in": "path",
+            "required": true
+          },
+          {
+            "type": "integer",
+            "format": "int64",
+            "description": "index of the pull request to get",
+            "name": "index",
+            "in": "path",
+            "required": true
+          },
+          {
+            "type": "string",
+            "description": "skip to given file",
+            "name": "skip-to",
+            "in": "query"
+          },
+          {
+            "enum": [
+              "ignore-all",
+              "ignore-change",
+              "ignore-eol",
+              "show-all"
+            ],
+            "type": "string",
+            "description": "whitespace behavior",
+            "name": "whitespace",
+            "in": "query"
+          },
+          {
+            "type": "integer",
+            "description": "page number of results to return (1-based)",
+            "name": "page",
+            "in": "query"
+          },
+          {
+            "type": "integer",
+            "description": "page size of results",
+            "name": "limit",
+            "in": "query"
+          }
+        ],
+        "responses": {
+          "200": {
+            "$ref": "#/responses/ChangedFileList"
+          },
+          "404": {
+            "$ref": "#/responses/notFound"
+          }
+        }
+      }
+    },
     "/repos/{owner}/{repo}/pulls/{index}/merge": {
       "get": {
         "produces": [
@@ -13715,6 +13789,52 @@
       },
       "x-go-package": "code.gitea.io/gitea/modules/structs"
     },
+    "ChangedFile": {
+      "description": "ChangedFile store information about files affected by the pull request",
+      "type": "object",
+      "properties": {
+        "additions": {
+          "type": "integer",
+          "format": "int64",
+          "x-go-name": "Additions"
+        },
+        "changes": {
+          "type": "integer",
+          "format": "int64",
+          "x-go-name": "Changes"
+        },
+        "contents_url": {
+          "type": "string",
+          "x-go-name": "ContentsURL"
+        },
+        "deletions": {
+          "type": "integer",
+          "format": "int64",
+          "x-go-name": "Deletions"
+        },
+        "filename": {
+          "type": "string",
+          "x-go-name": "Filename"
+        },
+        "html_url": {
+          "type": "string",
+          "x-go-name": "HTMLURL"
+        },
+        "previous_filename": {
+          "type": "string",
+          "x-go-name": "PreviousFilename"
+        },
+        "raw_url": {
+          "type": "string",
+          "x-go-name": "RawURL"
+        },
+        "status": {
+          "type": "string",
+          "x-go-name": "Status"
+        }
+      },
+      "x-go-package": "code.gitea.io/gitea/modules/structs"
+    },
     "CombinedStatus": {
       "description": "CombinedStatus holds the combined state of several statuses for a single commit",
       "type": "object",
@@ -19173,6 +19293,41 @@
         }
       }
     },
+    "ChangedFileList": {
+      "description": "ChangedFileList",
+      "schema": {
+        "type": "array",
+        "items": {
+          "$ref": "#/definitions/ChangedFile"
+        }
+      },
+      "headers": {
+        "X-HasMore": {
+          "type": "boolean",
+          "description": "True if there is another page"
+        },
+        "X-Page": {
+          "type": "integer",
+          "format": "int64",
+          "description": "The current page"
+        },
+        "X-PageCount": {
+          "type": "integer",
+          "format": "int64",
+          "description": "Total number of pages"
+        },
+        "X-PerPage": {
+          "type": "integer",
+          "format": "int64",
+          "description": "Commits per page"
+        },
+        "X-Total": {
+          "type": "integer",
+          "format": "int64",
+          "description": "Total commit count"
+        }
+      }
+    },
     "CombinedStatus": {
       "description": "CombinedStatus",
       "schema": {
diff --git a/tests/integration/api_pull_test.go b/tests/integration/api_pull_test.go
index 032912a07360a..8ce92f3d4a622 100644
--- a/tests/integration/api_pull_test.go
+++ b/tests/integration/api_pull_test.go
@@ -6,6 +6,7 @@ package integration
 
 import (
 	"fmt"
+	"io/ioutil"
 	"net/http"
 	"testing"
 
@@ -27,15 +28,35 @@ func TestAPIViewPulls(t *testing.T) {
 	repo := unittest.AssertExistsAndLoadBean(t, &repo_model.Repository{ID: 1})
 	owner := unittest.AssertExistsAndLoadBean(t, &user_model.User{ID: repo.OwnerID})
 
-	session := loginUser(t, "user2")
-	token := getTokenForLoggedInUser(t, session)
-	req := NewRequestf(t, "GET", "/api/v1/repos/%s/%s/pulls?state=all&token="+token, owner.Name, repo.Name)
-	resp := session.MakeRequest(t, req, http.StatusOK)
+	ctx := NewAPITestContext(t, "user2", repo.Name)
+
+	req := NewRequestf(t, "GET", "/api/v1/repos/%s/%s/pulls?state=all&token="+ctx.Token, owner.Name, repo.Name)
+	resp := ctx.Session.MakeRequest(t, req, http.StatusOK)
 
 	var pulls []*api.PullRequest
 	DecodeJSON(t, resp, &pulls)
 	expectedLen := unittest.GetCount(t, &issues_model.Issue{RepoID: repo.ID}, unittest.Cond("is_pull = ?", true))
 	assert.Len(t, pulls, expectedLen)
+
+	pull := pulls[0]
+	if assert.EqualValues(t, 5, pull.ID) {
+		resp = ctx.Session.MakeRequest(t, NewRequest(t, "GET", pull.DiffURL), http.StatusOK)
+		_, err := ioutil.ReadAll(resp.Body)
+		assert.NoError(t, err)
+		// TODO: use diff to generate stats to test against
+
+		t.Run(fmt.Sprintf("APIGetPullFiles_%d", pull.ID),
+			doAPIGetPullFiles(ctx, pull, func(t *testing.T, files []*api.ChangedFile) {
+				if assert.Len(t, files, 1) {
+					assert.EqualValues(t, "File-WoW", files[0].Filename)
+					assert.EqualValues(t, "", files[0].PreviousFilename)
+					assert.EqualValues(t, 1, files[0].Additions)
+					assert.EqualValues(t, 1, files[0].Changes)
+					assert.EqualValues(t, 0, files[0].Deletions)
+					assert.EqualValues(t, "added", files[0].Status)
+				}
+			}))
+	}
 }
 
 // TestAPIMergePullWIP ensures that we can't merge a WIP pull request
@@ -183,3 +204,22 @@ func TestAPIEditPull(t *testing.T) {
 	})
 	session.MakeRequest(t, req, http.StatusNotFound)
 }
+
+func doAPIGetPullFiles(ctx APITestContext, pr *api.PullRequest, callback func(*testing.T, []*api.ChangedFile)) func(*testing.T) {
+	return func(t *testing.T) {
+		url := fmt.Sprintf("/api/v1/repos/%s/%s/pulls/%d/files?token=%s", ctx.Username, ctx.Reponame, pr.Index, ctx.Token)
+
+		req := NewRequest(t, http.MethodGet, url)
+		if ctx.ExpectedCode == 0 {
+			ctx.ExpectedCode = http.StatusOK
+		}
+		resp := ctx.Session.MakeRequest(t, req, ctx.ExpectedCode)
+
+		files := make([]*api.ChangedFile, 0, 1)
+		DecodeJSON(t, resp, &files)
+
+		if callback != nil {
+			callback(t, files)
+		}
+	}
+}