diff --git a/.Rbuildignore b/.Rbuildignore
index e06c843..8051313 100644
--- a/.Rbuildignore
+++ b/.Rbuildignore
@@ -3,6 +3,7 @@
 ^\.Rproj\.user$
 ^\.git$
 ^\.github$
+^codecov\.yml$
 ^LICENSE\.md$
 ^\.claude$
 ^CLAUDE\.md$
diff --git a/.github/workflows/test-coverage.yaml b/.github/workflows/test-coverage.yaml
new file mode 100644
index 0000000..0b00e9f
--- /dev/null
+++ b/.github/workflows/test-coverage.yaml
@@ -0,0 +1,74 @@
+# Workflow derived from https://github.com/r-lib/actions/tree/v2/examples
+# Test coverage via covr, uploaded to Codecov. Python is provided the same way
+# R-CMD-check.yaml does -- through reticulate's managed miniconda -- so coverage
+# exercises the same kind of interpreter nat.python is designed to manage.
+on:
+  push:
+    branches: [main, master]
+  pull_request:
+  workflow_dispatch:
+
+name: test-coverage
+
+permissions: read-all
+
+jobs:
+  test-coverage:
+    runs-on: ubuntu-latest
+    env:
+      GITHUB_PAT: ${{ secrets.GITHUB_TOKEN }}
+      CODECOV_TOKEN: ${{ secrets.CODECOV_TOKEN }}
+    steps:
+      - uses: actions/checkout@v4
+
+      - uses: r-lib/actions/setup-r@v2
+        with:
+          use-public-rspm: true
+
+      - uses: r-lib/actions/setup-r-dependencies@v2
+        with:
+          extra-packages: any::covr, any::xml2
+          needs: coverage
+
+      - name: Provision Python (reticulate miniconda) and install nat.python
+        # Mirrors R-CMD-check.yaml's default leg: reticulate's own miniconda,
+        # numpy + pandas installed, then pin RETICULATE_PYTHON to that exact
+        # interpreter for the coverage run.
+        shell: Rscript {0}
+        run: |
+          reticulate::install_miniconda()
+          reticulate::py_install(c("numpy", "pandas"))
+          pak::local_install()
+          cat(sprintf("RETICULATE_PYTHON=%s\n", reticulate::py_config()$python),
+              file = Sys.getenv("GITHUB_ENV"), append = TRUE)
+
+      - name: Test coverage
+        shell: Rscript {0}
+        run: |
+          cov <- covr::package_coverage(
+            quiet = FALSE,
+            clean = FALSE,
+            install_path = file.path(normalizePath(Sys.getenv("RUNNER_TEMP"), winslash = "/"), "package")
+          )
+          covr::to_cobertura(cov)
+
+      - uses: codecov/codecov-action@v4
+        with:
+          fail_ci_if_error: false
+          file: ./cobertura.xml
+          plugin: noop
+          disable_search: true
+          token: ${{ secrets.CODECOV_TOKEN }}
+
+      - name: Show testthat output
+        if: always()
+        shell: bash
+        run: |
+          find '${{ runner.temp }}/package' -name 'testthat.Rout*' -exec cat '{}' \; || true
+
+      - name: Upload test results
+        if: failure()
+        uses: actions/upload-artifact@v4
+        with:
+          name: coverage-test-failures
+          path: ${{ runner.temp }}/package
diff --git a/DESCRIPTION b/DESCRIPTION
index c9f8a3d..c242a9b 100644
--- a/DESCRIPTION
+++ b/DESCRIPTION
@@ -32,7 +32,8 @@ Suggests:
     arrow,
     tibble,
     testthat (>= 3.0.0),
-    withr
+    withr,
+    covr
 Config/testthat/edition: 3
 Roxygen: list(markdown = TRUE)
 URL: https://github.com/flyconnectome/nat.python
diff --git a/README.md b/README.md
index 4dcd211..55a278e 100644
--- a/README.md
+++ b/README.md
@@ -3,6 +3,7 @@
 <!-- badges: start -->
 [![Lifecycle: experimental](https://img.shields.io/badge/lifecycle-experimental-orange.svg)](https://lifecycle.r-lib.org/articles/stages.html#experimental)
 [![R-CMD-check](https://github.com/flyconnectome/nat.python/actions/workflows/R-CMD-check.yaml/badge.svg)](https://github.com/flyconnectome/nat.python/actions/workflows/R-CMD-check.yaml)
+[![Codecov test coverage](https://codecov.io/gh/flyconnectome/nat.python/graph/badge.svg)](https://app.codecov.io/gh/flyconnectome/nat.python)
 <!-- badges: end -->
 
 > **⚠️ Design-phase package.** nat.python is being extracted from
diff --git a/codecov.yml b/codecov.yml
new file mode 100644
index 0000000..bfdc987
--- /dev/null
+++ b/codecov.yml
@@ -0,0 +1,8 @@
+coverage:
+  status:
+    project:
+      default:
+        informational: true
+    patch:
+      default:
+        informational: true