diff --git a/python/prophet/diagnostics.py b/python/prophet/diagnostics.py
index 89f740c06..8848b12f7 100644
--- a/python/prophet/diagnostics.py
+++ b/python/prophet/diagnostics.py
@@ -399,6 +399,7 @@ def prophet_copy(m: _ModelT, cutoff: pd.Timestamp | None = None) -> _ModelT:
     m2.extra_regressors = deepcopy(m.extra_regressors)
     m2.seasonalities = deepcopy(m.seasonalities)
     m2.country_holidays = deepcopy(m.country_holidays)
+    m2.fit_kwargs = deepcopy(m.fit_kwargs)
     return m2
 
 
diff --git a/python/prophet/tests/test_diagnostics.py b/python/prophet/tests/test_diagnostics.py
index f8bd7b507..2c7294664 100644
--- a/python/prophet/tests/test_diagnostics.py
+++ b/python/prophet/tests/test_diagnostics.py
@@ -593,6 +593,15 @@ def test_prophet_copy_scaling(self, data, backend):
         m2 = diagnostics.prophet_copy(m1)
         assert m2.scaling == "minmax"
 
+    def test_prophet_copy_fit_kwargs(self, data, backend):
+        m1 = Prophet(stan_backend=backend)
+        m1.history = m1.setup_dataframe(data.copy(), initialize_scales=True)
+        m1.fit_kwargs = {"iter": 500, "algorithm": "Newton"}
+        m2 = diagnostics.prophet_copy(m1)
+        assert m2.fit_kwargs == {"iter": 500, "algorithm": "Newton"}
+        m2.fit_kwargs["iter"] = 1000
+        assert m1.fit_kwargs["iter"] == 500
+
     def test_prophet_copy_custom(self, data, backend):
         changepoints = pd.date_range("2012-06-15", "2012-09-15")
         cutoff = pd.Timestamp("2012-07-25")