diff --git a/.changeset/fix-cause-tojson-key.md b/.changeset/fix-cause-tojson-key.md
new file mode 100644
index 00000000000..b86813affda
--- /dev/null
+++ b/.changeset/fix-cause-tojson-key.md
@@ -0,0 +1,5 @@
+---
+"effect": patch
+---
+
+fix(Cause): align toJSON key with actual property name
diff --git a/packages/effect/src/internal/cause.ts b/packages/effect/src/internal/cause.ts
index e557a914235..cfdf8a999f4 100644
--- a/packages/effect/src/internal/cause.ts
+++ b/packages/effect/src/internal/cause.ts
@@ -60,7 +60,7 @@ const proto = {
       case "Interrupt":
         return { _id: "Cause", _tag: this._tag, fiberId: this.fiberId.toJSON() }
       case "Fail":
-        return { _id: "Cause", _tag: this._tag, failure: toJSON(this.error) }
+        return { _id: "Cause", _tag: this._tag, error: toJSON(this.error) }
       case "Sequential":
       case "Parallel":
         return { _id: "Cause", _tag: this._tag, left: toJSON(this.left), right: toJSON(this.right) }
diff --git a/packages/effect/test/Cause.test.ts b/packages/effect/test/Cause.test.ts
index 0220598384a..a409909442d 100644
--- a/packages/effect/test/Cause.test.ts
+++ b/packages/effect/test/Cause.test.ts
@@ -123,7 +123,7 @@ describe("Cause", () => {
         expectJSON(Cause.fail(Option.some(1)), {
           _id: "Cause",
           _tag: "Fail",
-          failure: {
+          error: {
             _id: "Option",
             _tag: "Some",
             value: 1
@@ -189,12 +189,12 @@ describe("Cause", () => {
           left: {
             _id: "Cause",
             _tag: "Fail",
-            failure: "failure 1"
+            error: "failure 1"
           },
           right: {
             _id: "Cause",
             _tag: "Fail",
-            failure: "failure 2"
+            error: "failure 2"
           }
         })
       })
@@ -206,12 +206,12 @@ describe("Cause", () => {
           left: {
             _id: "Cause",
             _tag: "Fail",
-            failure: "failure 1"
+            error: "failure 1"
           },
           right: {
             _id: "Cause",
             _tag: "Fail",
-            failure: "failure 2"
+            error: "failure 2"
           }
         })
       })