diff --git a/finrl/agents/stablebaselines3/models.py b/finrl/agents/stablebaselines3/models.py
index f8ae8f39ca..1d2346adb4 100644
--- a/finrl/agents/stablebaselines3/models.py
+++ b/finrl/agents/stablebaselines3/models.py
@@ -1,7 +1,6 @@
 # DRL models from Stable Baselines 3
 from __future__ import annotations
 
-import statistics
 import time
 
 import numpy as np
@@ -56,23 +55,30 @@ def _on_step(self) -> bool:
         return True
 
     def _on_rollout_end(self) -> bool:
-        try:
-            rollout_buffer_rewards = self.locals["rollout_buffer"].rewards.flatten()
-            self.logger.record(
-                key="train/reward_min", value=min(rollout_buffer_rewards)
-            )
-            self.logger.record(
-                key="train/reward_mean", value=statistics.mean(rollout_buffer_rewards)
-            )
-            self.logger.record(
-                key="train/reward_max", value=max(rollout_buffer_rewards)
-            )
-        except BaseException as error:
-            # Handle the case where "rewards" is not found
-            self.logger.record(key="train/reward_min", value=None)
-            self.logger.record(key="train/reward_mean", value=None)
-            self.logger.record(key="train/reward_max", value=None)
-            print("Logging Error:", error)
+        # On-policy algorithms (A2C, PPO) expose a ``rollout_buffer``; off-policy
+        # algorithms (DDPG, TD3, SAC) expose a ``replay_buffer``. A model has
+        # exactly one of them, so read whichever is present instead of assuming
+        # ``rollout_buffer`` -- the previous code raised a KeyError for off-policy
+        # algorithms and logged empty (None) reward stats every rollout (#1395).
+        buffer = getattr(self.model, "rollout_buffer", None) or getattr(
+            self.model, "replay_buffer", None
+        )
+        if buffer is None:
+            return True
+
+        rewards = np.asarray(buffer.rewards)
+        # A replay buffer is not full early in training; only its first ``pos``
+        # rows hold real transitions, so drop the zero-initialized tail to keep
+        # the reward statistics meaningful.
+        if not getattr(buffer, "full", False):
+            rewards = rewards[: getattr(buffer, "pos", 0)]
+        rewards = rewards.flatten()
+        if rewards.size == 0:
+            return True
+
+        self.logger.record(key="train/reward_min", value=float(rewards.min()))
+        self.logger.record(key="train/reward_mean", value=float(rewards.mean()))
+        self.logger.record(key="train/reward_max", value=float(rewards.max()))
         return True
 
 
diff --git a/unit_tests/test_tensorboard_callback.py b/unit_tests/test_tensorboard_callback.py
new file mode 100644
index 0000000000..df4f8a3a12
--- /dev/null
+++ b/unit_tests/test_tensorboard_callback.py
@@ -0,0 +1,94 @@
+from __future__ import annotations
+
+import numpy as np
+
+from finrl.agents.stablebaselines3.models import TensorboardCallback
+
+
+class _FakeLogger:
+    """Capture ``logger.record(key, value)`` calls made by the callback."""
+
+    def __init__(self):
+        self.records = {}
+
+    def record(self, key, value):
+        self.records[key] = value
+
+
+class _FakeBuffer:
+    """Minimal stand-in for an SB3 rollout/replay buffer.
+
+    ``rewards`` has shape ``(buffer_size, n_envs)`` like the real buffers.
+    ``full``/``pos`` mirror SB3's fill bookkeeping so we can exercise the
+    partially-filled replay-buffer case.
+    """
+
+    def __init__(self, rewards, pos=None, full=True):
+        self.rewards = np.asarray(rewards, dtype=np.float32)
+        self.full = full
+        self.pos = self.rewards.shape[0] if pos is None else pos
+
+
+class _FakeModel:
+    """An SB3-like model exposing exactly one buffer plus a logger."""
+
+    def __init__(self, rollout_buffer=None, replay_buffer=None):
+        self.logger = _FakeLogger()
+        if rollout_buffer is not None:
+            self.rollout_buffer = rollout_buffer
+        if replay_buffer is not None:
+            self.replay_buffer = replay_buffer
+
+
+def _callback_for(model):
+    callback = TensorboardCallback()
+    callback.model = model  # `callback.logger` is a property -> model.logger
+    return callback
+
+
+def test_on_rollout_end_logs_on_policy_rollout_buffer():
+    # A2C/PPO expose a rollout_buffer that is full at the end of a rollout.
+    model = _FakeModel(rollout_buffer=_FakeBuffer([[1.0], [2.0], [3.0]]))
+    _callback_for(model)._on_rollout_end()
+
+    records = model.logger.records
+    assert records["train/reward_min"] == 1.0
+    assert records["train/reward_mean"] == 2.0
+    assert records["train/reward_max"] == 3.0
+
+
+def test_on_rollout_end_logs_off_policy_replay_buffer():
+    # Regression for #1395: DDPG/TD3/SAC expose a replay_buffer rather than a
+    # rollout_buffer. The old code assumed rollout_buffer, raising a KeyError
+    # and logging None values for every off-policy rollout.
+    model = _FakeModel(replay_buffer=_FakeBuffer([[10.0], [20.0], [30.0]]))
+    _callback_for(model)._on_rollout_end()
+
+    records = model.logger.records
+    assert records["train/reward_min"] == 10.0
+    assert records["train/reward_mean"] == 20.0
+    assert records["train/reward_max"] == 30.0
+    assert None not in records.values()
+
+
+def test_on_rollout_end_ignores_unfilled_replay_buffer_tail():
+    # A replay buffer is allocated up front; only its first ``pos`` rows hold
+    # real transitions until it fills, so the zero tail must be ignored.
+    model = _FakeModel(
+        replay_buffer=_FakeBuffer([[5.0], [7.0], [0.0], [0.0]], pos=2, full=False)
+    )
+    _callback_for(model)._on_rollout_end()
+
+    records = model.logger.records
+    assert records["train/reward_min"] == 5.0
+    assert records["train/reward_max"] == 7.0
+    assert records["train/reward_mean"] == 6.0
+
+
+def test_on_rollout_end_without_buffer_is_noop():
+    # Defensive: a model exposing neither buffer must not raise or log.
+    model = _FakeModel()
+    callback = _callback_for(model)
+
+    assert callback._on_rollout_end() is True
+    assert model.logger.records == {}