diff --git a/.changelog/20386.txt b/.changelog/20386.txt
new file mode 100644
index 000000000000..617280584a84
--- /dev/null
+++ b/.changelog/20386.txt
@@ -0,0 +1,3 @@
+```release-note:bug
+resource/aws_cognito_user_pool: Fixes error when `schema` has empty `string_attribute_constraints` or `number_attribute_constraints`
+```
diff --git a/internal/service/cognitoidp/user_pool.go b/internal/service/cognitoidp/user_pool.go
index 3ee923d33ae1..a80454d1272c 100644
--- a/internal/service/cognitoidp/user_pool.go
+++ b/internal/service/cognitoidp/user_pool.go
@@ -4,6 +4,7 @@
 package cognitoidp
 
 import (
+	"bytes"
 	"context"
 	"fmt"
 	"log"
@@ -20,6 +21,7 @@ import (
 	"github.com/hashicorp/terraform-plugin-sdk/v2/helper/schema"
 	"github.com/hashicorp/terraform-plugin-sdk/v2/helper/validation"
 	"github.com/hashicorp/terraform-provider-aws/internal/conns"
+	"github.com/hashicorp/terraform-provider-aws/internal/create"
 	"github.com/hashicorp/terraform-provider-aws/internal/enum"
 	"github.com/hashicorp/terraform-provider-aws/internal/errs"
 	"github.com/hashicorp/terraform-provider-aws/internal/errs/sdkdiag"
@@ -422,6 +424,7 @@ func resourceUserPool() *schema.Resource {
 				Optional: true,
 				MinItems: 1,
 				MaxItems: 50,
+				Set:      resourceUserPoolSchemaHash,
 				Elem: &schema.Resource{
 					Schema: map[string]*schema.Schema{
 						"attribute_data_type": {
@@ -1693,7 +1696,11 @@ func expandSchemaAttributeTypes(tfList []interface{}) []awstypes.SchemaAttribute
 						sact.MinLength = aws.String(v.(string))
 					}
 
-					apiObject.StringAttributeConstraints = sact
+					if sact.MinLength == nil && sact.MaxLength == nil {
+						apiObject.StringAttributeConstraints = nil
+					} else {
+						apiObject.StringAttributeConstraints = sact
+					}
 				}
 			}
 		}
@@ -2279,3 +2286,50 @@ func userPoolSchemaAttributeMatchesStandardAttribute(apiObject *awstypes.SchemaA
 
 	return false
 }
+
+func resourceUserPoolSchemaHash(v any) int {
+	var buf bytes.Buffer
+	m := v.(map[string]any)
+	buf.WriteString(fmt.Sprintf("%s-", m[names.AttrName].(string)))
+	buf.WriteString(fmt.Sprintf("%s-", m["attribute_data_type"].(string)))
+	buf.WriteString(fmt.Sprintf("%t-", m["developer_only_attribute"].(bool)))
+	buf.WriteString(fmt.Sprintf("%t-", m["mutable"].(bool)))
+	buf.WriteString(fmt.Sprintf("%t-", m["required"].(bool)))
+
+	if v, ok := m["string_attribute_constraints"]; ok {
+		data := v.([]any)
+
+		if len(data) > 0 {
+			buf.WriteString("string_attribute_constraints-")
+			m, _ := data[0].(map[string]any)
+			if ok {
+				if l, ok := m["min_length"]; ok && l.(string) != "" {
+					buf.WriteString(fmt.Sprintf("%s-", l.(string)))
+				}
+
+				if l, ok := m["max_length"]; ok && l.(string) != "" {
+					buf.WriteString(fmt.Sprintf("%s-", l.(string)))
+				}
+			}
+		}
+	}
+
+	if v, ok := m["number_attribute_constraints"]; ok {
+		data := v.([]any)
+
+		if len(data) > 0 {
+			buf.WriteString("number_attribute_constraints-")
+			m, _ := data[0].(map[string]any)
+			if ok {
+				if l, ok := m["min_value"]; ok && l.(string) != "" {
+					buf.WriteString(fmt.Sprintf("%s-", l.(string)))
+				}
+
+				if l, ok := m["max_value"]; ok && l.(string) != "" {
+					buf.WriteString(fmt.Sprintf("%s-", l.(string)))
+				}
+			}
+		}
+	}
+	return create.StringHashcode(buf.String())
+}
diff --git a/internal/service/cognitoidp/user_pool_test.go b/internal/service/cognitoidp/user_pool_test.go
index fce568c49469..be19a8a58a6e 100644
--- a/internal/service/cognitoidp/user_pool_test.go
+++ b/internal/service/cognitoidp/user_pool_test.go
@@ -1389,7 +1389,7 @@ func TestAccCognitoIDPUserPool_schemaAttributes(t *testing.T) {
 				Config: testAccUserPoolConfig_schemaAttributes(rName),
 				Check: resource.ComposeAggregateTestCheckFunc(
 					testAccCheckUserPoolExists(ctx, resourceName, &pool1),
-					resource.TestCheckResourceAttr(resourceName, "schema.#", acctest.Ct2),
+					resource.TestCheckResourceAttr(resourceName, "schema.#", acctest.Ct4),
 					resource.TestCheckTypeSetElemNestedAttrs(resourceName, "schema.*", map[string]string{
 						"attribute_data_type":                       "String",
 						"developer_only_attribute":                  acctest.CtFalse,
@@ -1410,14 +1410,31 @@ func TestAccCognitoIDPUserPool_schemaAttributes(t *testing.T) {
 						"required":                       acctest.CtFalse,
 						"string_attribute_constraints.#": acctest.Ct0,
 					}),
-				),
+					resource.TestCheckTypeSetElemNestedAttrs(resourceName, "schema.*", map[string]string{
+						"attribute_data_type":            "String",
+						"developer_only_attribute":       acctest.CtFalse,
+						"mutable":                        acctest.CtTrue,
+						names.AttrName:                   "strattr",
+						"number_attribute_constraints.#": acctest.Ct0,
+						"required":                       acctest.CtFalse,
+						"string_attribute_constraints.#": acctest.Ct1,
+					}),
+					resource.TestCheckTypeSetElemNestedAttrs(resourceName, "schema.*", map[string]string{
+						"attribute_data_type":            "Number",
+						"developer_only_attribute":       acctest.CtFalse,
+						"mutable":                        acctest.CtTrue,
+						names.AttrName:                   "numattr",
+						"required":                       acctest.CtFalse,
+						"number_attribute_constraints.#": acctest.Ct1,
+						"string_attribute_constraints.#": acctest.Ct0,
+					})),
 			},
 			{
 				Config: testAccUserPoolConfig_schemaAttributesUpdated(rName, "mybool"),
 				Check: resource.ComposeAggregateTestCheckFunc(
 					testAccCheckUserPoolExists(ctx, resourceName, &pool2),
 					testAccCheckUserPoolNotRecreated(&pool1, &pool2),
-					resource.TestCheckResourceAttr(resourceName, "schema.#", acctest.Ct3),
+					resource.TestCheckResourceAttr(resourceName, "schema.#", "5"),
 					resource.TestCheckTypeSetElemNestedAttrs(resourceName, "schema.*", map[string]string{
 						"attribute_data_type":                       "String",
 						"developer_only_attribute":                  acctest.CtFalse,
@@ -1449,12 +1466,36 @@ func TestAccCognitoIDPUserPool_schemaAttributes(t *testing.T) {
 						"required":                                 acctest.CtFalse,
 						"string_attribute_constraints.#":           acctest.Ct0,
 					}),
+					resource.TestCheckTypeSetElemNestedAttrs(resourceName, "schema.*", map[string]string{
+						"attribute_data_type":            "String",
+						"developer_only_attribute":       acctest.CtFalse,
+						"mutable":                        acctest.CtTrue,
+						names.AttrName:                   "strattr",
+						"number_attribute_constraints.#": acctest.Ct0,
+						"required":                       acctest.CtFalse,
+						"string_attribute_constraints.#": acctest.Ct1,
+					}),
+					resource.TestCheckTypeSetElemNestedAttrs(resourceName, "schema.*", map[string]string{
+						"attribute_data_type":            "Number",
+						"developer_only_attribute":       acctest.CtFalse,
+						"mutable":                        acctest.CtTrue,
+						names.AttrName:                   "numattr",
+						"required":                       acctest.CtFalse,
+						"number_attribute_constraints.#": acctest.Ct1,
+						"string_attribute_constraints.#": acctest.Ct0,
+					}),
 				),
 			},
 			{
 				ResourceName:      resourceName,
 				ImportState:       true,
 				ImportStateVerify: true,
+				ImportStateVerifyIgnore: []string{
+					"schema.2.number_attribute_constraints.0.max_value",
+					"schema.2.number_attribute_constraints.0.min_value",
+					"schema.4.string_attribute_constraints.0.max_length",
+					"schema.4.string_attribute_constraints.0.min_length",
+				},
 			},
 		},
 	})
@@ -2662,6 +2703,24 @@ resource "aws_cognito_user_pool" "test" {
     }
   }
 
+  schema {
+    attribute_data_type      = "String"
+    developer_only_attribute = false
+    mutable                  = true
+    name                     = "strattr"
+    required                 = false
+    string_attribute_constraints {}
+  }
+
+  schema {
+    attribute_data_type      = "Number"
+    developer_only_attribute = false
+    mutable                  = true
+    name                     = "numattr"
+    required                 = false
+    number_attribute_constraints {}
+  }
+
   schema {
     attribute_data_type      = "Boolean"
     developer_only_attribute = true
@@ -2691,6 +2750,24 @@ resource "aws_cognito_user_pool" "test" {
     }
   }
 
+  schema {
+    attribute_data_type      = "String"
+    developer_only_attribute = false
+    mutable                  = true
+    name                     = "strattr"
+    required                 = false
+    string_attribute_constraints {}
+  }
+
+  schema {
+    attribute_data_type      = "Number"
+    developer_only_attribute = false
+    mutable                  = true
+    name                     = "numattr"
+    required                 = false
+    number_attribute_constraints {}
+  }
+
   schema {
     attribute_data_type      = "Boolean"
     developer_only_attribute = true