diff --git a/crates/ruff_python_formatter/resources/test/fixtures/ruff/expression/lambda.py b/crates/ruff_python_formatter/resources/test/fixtures/ruff/expression/lambda.py
index 4a7090ff13..660d5644e9 100644
--- a/crates/ruff_python_formatter/resources/test/fixtures/ruff/expression/lambda.py
+++ b/crates/ruff_python_formatter/resources/test/fixtures/ruff/expression/lambda.py
@@ -228,3 +228,24 @@ def a():
         g = 10
     )
 
+(
+    lambda
+    * # comment 2
+    x:
+    x
+)
+
+(
+    lambda # comment 1
+    * # comment 2
+    x:
+    x
+)
+
+(
+    lambda # comment 1
+    y,
+    * # comment 2
+    x:
+    x
+)
diff --git a/crates/ruff_python_formatter/src/comments/placement.rs b/crates/ruff_python_formatter/src/comments/placement.rs
index f28f9b18a8..28397b6dcf 100644
--- a/crates/ruff_python_formatter/src/comments/placement.rs
+++ b/crates/ruff_python_formatter/src/comments/placement.rs
@@ -1816,7 +1816,7 @@ fn handle_lambda_comment<'a>(
     source: &str,
 ) -> CommentPlacement<'a> {
     if let Some(parameters) = lambda.parameters.as_deref() {
-        // Comments between the `lambda` and the parameters are dangling on the lambda:
+        // End-of-line comments between the `lambda` and the parameters are dangling on the lambda:
         // ```python
         // (
         //     lambda  # comment
@@ -1824,8 +1824,24 @@ fn handle_lambda_comment<'a>(
         //     y
         // )
         // ```
+        //
+        // But own-line comments are leading on the first parameter, if it exists:
+        // ```python
+        // (
+        //     lambda
+        //     # comment
+        //     x:
+        //     y
+        // )
+        // ```
         if comment.start() < parameters.start() {
-            return CommentPlacement::dangling(comment.enclosing_node(), comment);
+            return if let Some(first) = parameters.iter().next()
+                && comment.line_position().is_own_line()
+            {
+                CommentPlacement::leading(first.as_parameter(), comment)
+            } else {
+                CommentPlacement::dangling(comment.enclosing_node(), comment)
+            };
         }
 
         // Comments between the parameters and the body are dangling on the lambda:
diff --git a/crates/ruff_python_formatter/src/expression/expr_lambda.rs b/crates/ruff_python_formatter/src/expression/expr_lambda.rs
index c5890fba24..335f112323 100644
--- a/crates/ruff_python_formatter/src/expression/expr_lambda.rs
+++ b/crates/ruff_python_formatter/src/expression/expr_lambda.rs
@@ -32,7 +32,69 @@ impl FormatNodeRule<ExprLambda> for FormatExprLambda {
                 .split_at(dangling.partition_point(|comment| comment.end() < parameters.start()));
 
             if dangling_before_parameters.is_empty() {
-                write!(f, [space()])?;
+                // If the first parameter has a leading comment, insert a hard line break. This
+                // comment is associated as a leading comment on the first parameter:
+                //
+                // ```py
+                // (
+                //     lambda
+                //     * # comment
+                //     x:
+                //     x
+                // )
+                // ```
+                //
+                // so a hard line break is needed to avoid formatting it like:
+                //
+                // ```py
+                // (
+                //     lambda # comment
+                //     *x: x
+                // )
+                // ```
+                //
+                // which is unstable because it's missing the second space before the comment.
+                //
+                // Inserting the line break causes it to format like:
+                //
+                // ```py
+                // (
+                //     lambda
+                //     # comment
+                //     *x :x
+                // )
+                // ```
+                //
+                // which is also consistent with the formatting in the presence of an actual
+                // dangling comment on the lambda:
+                //
+                // ```py
+                // (
+                //     lambda # comment 1
+                //     * # comment 2
+                //     x:
+                //     x
+                // )
+                // ```
+                //
+                // formats to:
+                //
+                // ```py
+                // (
+                //     lambda  # comment 1
+                //     # comment 2
+                //     *x: x
+                // )
+                // ```
+                if parameters
+                    .iter()
+                    .next()
+                    .is_some_and(|parameter| comments.has_leading(parameter.as_parameter()))
+                {
+                    hard_line_break().fmt(f)?;
+                } else {
+                    write!(f, [space()])?;
+                }
             } else {
                 write!(f, [dangling_comments(dangling_before_parameters)])?;
             }
diff --git a/crates/ruff_python_formatter/tests/snapshots/format@expression__lambda.py.snap b/crates/ruff_python_formatter/tests/snapshots/format@expression__lambda.py.snap
index 03332c6f92..3009dfaefc 100644
--- a/crates/ruff_python_formatter/tests/snapshots/format@expression__lambda.py.snap
+++ b/crates/ruff_python_formatter/tests/snapshots/format@expression__lambda.py.snap
@@ -1,7 +1,6 @@
 ---
 source: crates/ruff_python_formatter/tests/fixtures.rs
 input_file: crates/ruff_python_formatter/resources/test/fixtures/ruff/expression/lambda.py
-snapshot_kind: text
 ---
 ## Input
 ```python
@@ -235,6 +234,27 @@ def a():
         g = 10
     )
 
+(
+    lambda
+    * # comment 2
+    x:
+    x
+)
+
+(
+    lambda # comment 1
+    * # comment 2
+    x:
+    x
+)
+
+(
+    lambda # comment 1
+    y,
+    * # comment 2
+    x:
+    x
+)
 ```
 
 ## Output
@@ -473,4 +493,24 @@ def a():
         g=2: d,
         g=10,
     )
+
+
+(
+    lambda
+    # comment 2
+    *x: x
+)
+
+(
+    lambda  # comment 1
+    # comment 2
+    *x: x
+)
+
+(
+    lambda  # comment 1
+    y,
+    # comment 2
+    *x: x
+)
 ```