diff --git a/brax/training/agents/ppo/networks.py b/brax/training/agents/ppo/networks.py
index 1410831f..70c5a1ca 100644
--- a/brax/training/agents/ppo/networks.py
+++ b/brax/training/agents/ppo/networks.py
@@ -14,6 +14,7 @@
 
 """PPO networks."""
 
+import warnings
 from typing import Any, Literal, Mapping, Sequence, Tuple
 
 from brax.training import distribution
@@ -116,6 +117,23 @@ def make_ppo_networks(
   value_kernel_init_kwargs = value_network_kernel_init_kwargs or {}
   mean_kernel_init_kwargs_ = mean_kernel_init_kwargs or {}
 
+  if distribution_type == 'tanh_normal':
+    ignored = []
+    if init_noise_std != 1.0:
+      ignored.append(f'init_noise_std={init_noise_std!r}')
+    if noise_std_type != 'scalar':
+      ignored.append(f'noise_std_type={noise_std_type!r}')
+    if state_dependent_std:
+      ignored.append(f'state_dependent_std={state_dependent_std!r}')
+    if ignored:
+      warnings.warn(
+          f'{", ".join(ignored)} {"has" if len(ignored) == 1 else "have"}'
+          ' no effect with distribution_type="tanh_normal". The standard'
+          ' deviation is determined entirely by the policy network output.'
+          ' These parameters only apply to distribution_type="normal".',
+          stacklevel=2,
+      )
+
   parametric_action_distribution: distribution.ParametricDistribution
   if distribution_type == 'normal':
     parametric_action_distribution = distribution.NormalDistribution(
@@ -163,4 +181,4 @@ def make_ppo_networks(
       policy_network=policy_network,
       value_network=value_network,
       parametric_action_distribution=parametric_action_distribution,
-  )
+  )
\ No newline at end of file