diff --git a/crates/ruff_cli/src/commands/format.rs b/crates/ruff_cli/src/commands/format.rs
index cddf59303d957c..6e6a7b752141fc 100644
--- a/crates/ruff_cli/src/commands/format.rs
+++ b/crates/ruff_cli/src/commands/format.rs
@@ -73,7 +73,7 @@ pub(crate) fn format(
     }
 
     let start = Instant::now();
-    let (results, errors): (Vec<_>, Vec<_>) = paths
+    let (mut results, mut errors): (Vec<_>, Vec<_>) = paths
         .into_par_iter()
         .filter_map(|entry| {
             match entry {
@@ -105,6 +105,27 @@ pub(crate) fn format(
         });
     let duration = start.elapsed();
 
+    // Make output deterministic, at least as long as we have a path
+    results.sort_by(|x, y| x.path.cmp(&y.path));
+    errors.sort_by(|x, y| {
+        fn get_key(error: &FormatCommandError) -> Option<&PathBuf> {
+            match &error {
+                FormatCommandError::Ignore(ignore) => {
+                    if let ignore::Error::WithPath { path, .. } = ignore {
+                        Some(path)
+                    } else {
+                        None
+                    }
+                }
+                FormatCommandError::Panic(path, _)
+                | FormatCommandError::Read(path, _)
+                | FormatCommandError::Format(path, _)
+                | FormatCommandError::Write(path, _) => path.as_ref(),
+            }
+        }
+        get_key(x).cmp(&get_key(y))
+    });
+
     debug!(
         "Formatted {} files in {:.2?}",
         results.len() + errors.len(),
diff --git a/crates/ruff_cli/tests/format.rs b/crates/ruff_cli/tests/format.rs
index 432eb86a0d0a16..b9e224bb7f9302 100644
--- a/crates/ruff_cli/tests/format.rs
+++ b/crates/ruff_cli/tests/format.rs
@@ -227,13 +227,6 @@ fn test_diff() {
         success: false
         exit_code: 1
         ----- stdout -----
-        --- resources/test/fixtures/unformatted.py
-        +++ resources/test/fixtures/unformatted.py
-        @@ -1,3 +1,3 @@
-         x = 1
-        -y=2
-        +y = 2
-         z = 3
         --- resources/test/fixtures/unformatted.ipynb
         +++ resources/test/fixtures/unformatted.ipynb
         @@ -1,3 +1,4 @@
@@ -243,6 +236,13 @@ fn test_diff() {
         +
         +maths = (numpy.arange(100) ** 2).sum()
         +stats = numpy.asarray([1, 2, 3, 4]).median()
+        --- resources/test/fixtures/unformatted.py
+        +++ resources/test/fixtures/unformatted.py
+        @@ -1,3 +1,3 @@
+         x = 1
+        -y=2
+        +y = 2
+         z = 3
 
         ----- stderr -----
         warning: `ruff format` is not yet stable, and subject to change in future versions.