diff --git a/providers/openfeature-provider-flagd/README.md b/providers/openfeature-provider-flagd/README.md
index 9cbb865e..fbade51f 100644
--- a/providers/openfeature-provider-flagd/README.md
+++ b/providers/openfeature-provider-flagd/README.md
@@ -81,7 +81,7 @@ The default options can be defined in the FlagdProvider constructor.
 |--------------------------|--------------------------------|----------------------------|-------------------------------|---------------------|
 | resolver_type            | FLAGD_RESOLVER                 | enum - `rpc`, `in-process` | rpc                           |                     |
 | host                     | FLAGD_HOST                     | str                        | localhost                     | rpc & in-process    |
-| port                     | FLAGD_PORT                     | int                        | 8013 (rpc), 8015 (in-process) | rpc & in-process    |
+| port                     | FLAGD_SYNC_PORT (in-process), FLAGD_PORT (rpc or fallback) | int                        | 8013 (rpc), 8015 (in-process) | rpc & in-process    |
 | tls                      | FLAGD_TLS                      | bool                       | false                         | rpc & in-process    |
 | cert_path                | FLAGD_SERVER_CERT_PATH         | String                     | null                          | rpc & in-process    |
 | deadline                 | FLAGD_DEADLINE_MS              | int                        | 500                           | rpc & in-process    |
diff --git a/providers/openfeature-provider-flagd/src/openfeature/contrib/provider/flagd/config.py b/providers/openfeature-provider-flagd/src/openfeature/contrib/provider/flagd/config.py
index 2a21ba36..f2feb648 100644
--- a/providers/openfeature-provider-flagd/src/openfeature/contrib/provider/flagd/config.py
+++ b/providers/openfeature-provider-flagd/src/openfeature/contrib/provider/flagd/config.py
@@ -42,6 +42,7 @@ class CacheType(Enum):
 ENV_VAR_OFFLINE_FLAG_SOURCE_PATH = "FLAGD_OFFLINE_FLAG_SOURCE_PATH"
 ENV_VAR_OFFLINE_POLL_MS = "FLAGD_OFFLINE_POLL_MS"
 ENV_VAR_PORT = "FLAGD_PORT"
+ENV_VAR_SYNC_PORT = "FLAGD_SYNC_PORT"
 ENV_VAR_RESOLVER_TYPE = "FLAGD_RESOLVER"
 ENV_VAR_RETRY_BACKOFF_MS = "FLAGD_RETRY_BACKOFF_MS"
 ENV_VAR_RETRY_BACKOFF_MAX_MS = "FLAGD_RETRY_BACKOFF_MAX_MS"
@@ -79,7 +80,7 @@ def env_or_default(
 
 @dataclasses.dataclass
 class Config:
-    def __init__(  # noqa: PLR0913
+    def __init__(  # noqa: PLR0913, PLR0915
         self,
         host: typing.Optional[str] = None,
         port: typing.Optional[int] = None,
@@ -149,17 +150,25 @@ def __init__(  # noqa: PLR0913
             else resolver
         )
 
-        default_port = (
-            DEFAULT_PORT_RPC
-            if self.resolver is ResolverType.RPC
-            else DEFAULT_PORT_IN_PROCESS
-        )
-
-        self.port: int = (
-            int(env_or_default(ENV_VAR_PORT, default_port, cast=int))
-            if port is None
-            else port
-        )
+        # Port configuration with FLAGD_SYNC_PORT support for in-process mode
+        if port is None:
+            if self.resolver is ResolverType.IN_PROCESS:
+                # For in-process: try FLAGD_SYNC_PORT, then FLAGD_PORT (backwards compatibility), then default
+                port_from_env = os.environ.get(ENV_VAR_SYNC_PORT) or os.environ.get(
+                    ENV_VAR_PORT
+                )
+                self.port = (
+                    int(port_from_env)
+                    if port_from_env is not None
+                    else DEFAULT_PORT_IN_PROCESS
+                )
+            else:
+                # For RPC: use FLAGD_PORT only
+                self.port = int(
+                    env_or_default(ENV_VAR_PORT, DEFAULT_PORT_RPC, cast=int)
+                )
+        else:
+            self.port = port
 
         self.offline_flag_source_path = (
             env_or_default(
diff --git a/providers/openfeature-provider-flagd/tests/test_config.py b/providers/openfeature-provider-flagd/tests/test_config.py
index 510009d0..a671f8c1 100644
--- a/providers/openfeature-provider-flagd/tests/test_config.py
+++ b/providers/openfeature-provider-flagd/tests/test_config.py
@@ -23,6 +23,7 @@
     ENV_VAR_PORT,
     ENV_VAR_RETRY_BACKOFF_MS,
     ENV_VAR_STREAM_DEADLINE_MS,
+    ENV_VAR_SYNC_PORT,
     ENV_VAR_TLS,
     CacheType,
     Config,
@@ -147,3 +148,56 @@ def test_uses_arguments_over_environments_and_defaults(monkeypatch, resolver_typ
     assert config.retry_backoff_ms == retry_backoff
     assert config.stream_deadline_ms == stream_deadline
     assert config.tls is tls
+
+
+def test_in_process_uses_sync_port(monkeypatch):
+    """Test that FLAGD_SYNC_PORT is used for in-process mode when set."""
+    sync_port = 9999
+    monkeypatch.setenv(ENV_VAR_SYNC_PORT, str(sync_port))
+
+    config = Config(resolver=ResolverType.IN_PROCESS)
+    assert config.port == sync_port
+    assert config.resolver == ResolverType.IN_PROCESS
+
+
+def test_in_process_fallback_to_port(monkeypatch):
+    """Test that FLAGD_PORT is used as fallback when FLAGD_SYNC_PORT is not set."""
+    port = 7777
+    monkeypatch.setenv(ENV_VAR_PORT, str(port))
+
+    config = Config(resolver=ResolverType.IN_PROCESS)
+    assert config.port == port
+    assert config.resolver == ResolverType.IN_PROCESS
+
+
+def test_in_process_sync_port_priority(monkeypatch):
+    """Test that FLAGD_SYNC_PORT takes priority over FLAGD_PORT when both are set."""
+    sync_port = 9999
+    port = 7777
+    monkeypatch.setenv(ENV_VAR_SYNC_PORT, str(sync_port))
+    monkeypatch.setenv(ENV_VAR_PORT, str(port))
+
+    config = Config(resolver=ResolverType.IN_PROCESS)
+    assert config.port == sync_port  # FLAGD_SYNC_PORT should win
+    assert config.resolver == ResolverType.IN_PROCESS
+
+
+def test_rpc_ignores_sync_port(monkeypatch):
+    """Test that RPC mode uses FLAGD_PORT and ignores FLAGD_SYNC_PORT."""
+    sync_port = 9999
+    port = 7777
+    monkeypatch.setenv(ENV_VAR_SYNC_PORT, str(sync_port))
+    monkeypatch.setenv(ENV_VAR_PORT, str(port))
+
+    config = Config(resolver=ResolverType.RPC)
+    assert config.port == port  # RPC should use FLAGD_PORT
+    assert config.resolver == ResolverType.RPC
+
+
+def test_in_process_default_port_when_no_env_var(monkeypatch):
+    """Test that in-process mode uses default port when neither env var is set."""
+    monkeypatch.delenv(ENV_VAR_SYNC_PORT, raising=False)
+    monkeypatch.delenv(ENV_VAR_PORT, raising=False)
+    config = Config(resolver=ResolverType.IN_PROCESS)
+    assert config.port == DEFAULT_PORT_IN_PROCESS
+    assert config.resolver == ResolverType.IN_PROCESS