diff --git a/.github/workflows/build.yml b/.github/workflows/build.yml
index bda6b056..3bf008b2 100644
--- a/.github/workflows/build.yml
+++ b/.github/workflows/build.yml
@@ -28,3 +28,9 @@ jobs:
         run: npm run lint
       - name: Test
         run: npm run test:ci
+      - name: Upload coverage reports to Codecov
+        uses: codecov/codecov-action@v4.0.1
+        with:
+          token: ${{ secrets.CODECOV_TOKEN }}
+          slug: Quramy/pico-ml
+          files: ./coverage/coverage-final.json
diff --git a/README.md b/README.md
index 232b06e1..022c3392 100644
--- a/README.md
+++ b/README.md
@@ -2,6 +2,7 @@
 
 [![github actions](https://github.com/Quramy/pico-ml/workflows/build/badge.svg)](https://github.com/Quramy/pico-ml/actions)
 [![npm version](https://badge.fury.io/js/pico-ml.svg)](https://badge.fury.io/js/pico-ml)
+[![codecov](https://codecov.io/gh/Quramy/pico-ml/graph/badge.svg?token=ZZN2OX50UX)](https://codecov.io/gh/Quramy/pico-ml)
 
 A toy programming language which is a subset of OCaml.