diff --git a/arro3-compute/src/lib.rs b/arro3-compute/src/lib.rs
index 9049ea6..d8d77b3 100644
--- a/arro3-compute/src/lib.rs
+++ b/arro3-compute/src/lib.rs
@@ -1,4 +1,7 @@
+use pyo3::exceptions::PyRuntimeWarning;
+use pyo3::intern;
 use pyo3::prelude::*;
+use pyo3::types::PyTuple;
 
 mod aggregate;
 mod arith;
@@ -17,8 +20,26 @@ fn ___version() -> &'static str {
     VERSION
 }
 
+/// Raise RuntimeWarning for debug builds
+#[pyfunction]
+fn check_debug_build(py: Python) -> PyResult<()> {
+    #[cfg(debug_assertions)]
+    {
+        let warnings_mod = py.import_bound(intern!(py, "warnings"))?;
+        let warning = PyRuntimeWarning::new_err(
+            "arro3.compute has not been compiled in release mode. Performance will be degraded.",
+        );
+        let args = PyTuple::new_bound(py, vec![warning.into_py(py)]);
+        warnings_mod.call_method1(intern!(py, "warn"), args)?;
+    }
+
+    Ok(())
+}
+
 #[pymodule]
-fn _compute(_py: Python, m: &Bound<PyModule>) -> PyResult<()> {
+fn _compute(py: Python, m: &Bound<PyModule>) -> PyResult<()> {
+    check_debug_build(py)?;
+
     m.add_wrapped(wrap_pyfunction!(___version))?;
 
     m.add_wrapped(wrap_pyfunction!(aggregate::max))?;
diff --git a/arro3-core/src/lib.rs b/arro3-core/src/lib.rs
index 168bea5..936310f 100644
--- a/arro3-core/src/lib.rs
+++ b/arro3-core/src/lib.rs
@@ -1,4 +1,7 @@
+use pyo3::exceptions::PyRuntimeWarning;
+use pyo3::intern;
 use pyo3::prelude::*;
+use pyo3::types::PyTuple;
 
 mod accessors;
 mod constructors;
@@ -10,9 +13,27 @@ fn ___version() -> &'static str {
     VERSION
 }
 
+/// Raise RuntimeWarning for debug builds
+#[pyfunction]
+fn check_debug_build(py: Python) -> PyResult<()> {
+    #[cfg(debug_assertions)]
+    {
+        let warnings_mod = py.import_bound(intern!(py, "warnings"))?;
+        let warning = PyRuntimeWarning::new_err(
+            "arro3.core has not been compiled in release mode. Performance will be degraded.",
+        );
+        let args = PyTuple::new_bound(py, vec![warning.into_py(py)]);
+        warnings_mod.call_method1(intern!(py, "warn"), args)?;
+    }
+
+    Ok(())
+}
+
 /// A Python module implemented in Rust.
 #[pymodule]
-fn _core(_py: Python, m: &Bound<PyModule>) -> PyResult<()> {
+fn _core(py: Python, m: &Bound<PyModule>) -> PyResult<()> {
+    check_debug_build(py)?;
+
     m.add_wrapped(wrap_pyfunction!(___version))?;
 
     m.add_class::<pyo3_arrow::PyArray>()?;
diff --git a/arro3-io/src/lib.rs b/arro3-io/src/lib.rs
index 23d1beb..3705acf 100644
--- a/arro3-io/src/lib.rs
+++ b/arro3-io/src/lib.rs
@@ -1,4 +1,7 @@
+use pyo3::exceptions::PyRuntimeWarning;
+use pyo3::intern;
 use pyo3::prelude::*;
+use pyo3::types::PyTuple;
 
 mod csv;
 mod error;
@@ -14,8 +17,26 @@ fn ___version() -> &'static str {
     VERSION
 }
 
+/// Raise RuntimeWarning for debug builds
+#[pyfunction]
+fn check_debug_build(py: Python) -> PyResult<()> {
+    #[cfg(debug_assertions)]
+    {
+        let warnings_mod = py.import_bound(intern!(py, "warnings"))?;
+        let warning = PyRuntimeWarning::new_err(
+            "arro3.io has not been compiled in release mode. Performance will be degraded.",
+        );
+        let args = PyTuple::new_bound(py, vec![warning.into_py(py)]);
+        warnings_mod.call_method1(intern!(py, "warn"), args)?;
+    }
+
+    Ok(())
+}
+
 #[pymodule]
 fn _io(py: Python, m: &Bound<PyModule>) -> PyResult<()> {
+    check_debug_build(py)?;
+
     m.add_wrapped(wrap_pyfunction!(___version))?;
 
     pyo3_object_store::register_store_module(py, m, "arro3.io")?;