diff --git a/CHANGELOG.md b/CHANGELOG.md
index 0ea1ade65..bd721d66f 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -24,6 +24,7 @@ Remember to align the itemized text with the first line of an item within a list
   * The option `--jax_coordination_service` has been removed. It is now always
     `True`.
   * `jax.jaxpr_util` has been removed from the public JAX namespace.
+  * `JAX_USE_PJRT_C_API_ON_TPU` no longer has an effect (i.e. it always defaults to true).
 
 * Internal deprecations:
   * The internal utilities `jax.core.is_opaque_dtype` and `jax.core.has_opaque_dtype`
diff --git a/jax/_src/cloud_tpu_init.py b/jax/_src/cloud_tpu_init.py
index 7ecd13308..e1cb601b1 100644
--- a/jax/_src/cloud_tpu_init.py
+++ b/jax/_src/cloud_tpu_init.py
@@ -69,12 +69,10 @@ def cloud_tpu_init() -> None:
   os.environ.setdefault('JAX_PLATFORMS', 'tpu,cpu')
   os.environ['TPU_ML_PLATFORM'] = 'JAX'
 
-  if 'JAX_USE_PJRT_C_API_ON_TPU' not in os.environ:
-    os.environ['JAX_USE_PJRT_C_API_ON_TPU'] = 'true'
-
-  use_pjrt_c_api = os.environ['JAX_USE_PJRT_C_API_ON_TPU']
-  if use_pjrt_c_api in ("false", "0"):
+  # TODO(skyewm): remove this warning at some point, say around Sept 2023.
+  use_pjrt_c_api = os.environ.get('JAX_USE_PJRT_C_API_ON_TPU', None)
+  if use_pjrt_c_api:
     warnings.warn(
-        f"JAX_USE_PJRT_C_API_ON_TPU={use_pjrt_c_api} will no longer be "
-        "supported in an upcoming future release. Please file an issue at "
-        "https://github.com/google/jax/issues if you need this setting.")
+        "JAX_USE_PJRT_C_API_ON_TPU no longer has an effect (the new TPU "
+        "runtime is always enabled now). Unset the environment variable "
+        "to disable this warning.")