diff --git a/stack_orchestrator/deploy/k8s/cluster_info.py b/stack_orchestrator/deploy/k8s/cluster_info.py
index ae0cb24d..da24bdc2 100644
--- a/stack_orchestrator/deploy/k8s/cluster_info.py
+++ b/stack_orchestrator/deploy/k8s/cluster_info.py
@@ -31,6 +31,7 @@ from stack_orchestrator.deploy.k8s.helpers import (
     envs_from_environment_variables_map,
     envs_from_compose_file,
     merge_envs,
+    translate_sidecar_service_names,
 )
 from stack_orchestrator.deploy.deploy_util import (
     parsed_pod_files_map_from_file_names,
@@ -439,6 +440,12 @@ class ClusterInfo:
                     if "environment" in service_info
                     else self.environment_variables.map
                 )
+                # Translate docker-compose service names to localhost for sidecars
+                # All services in the same pod share the network namespace
+                sibling_services = [s for s in services.keys() if s != service_name]
+                merged_envs = translate_sidecar_service_names(
+                    merged_envs, sibling_services
+                )
                 envs = envs_from_environment_variables_map(merged_envs)
                 if opts.o.debug:
                     print(f"Merged envs: {envs}")
diff --git a/stack_orchestrator/deploy/k8s/helpers.py b/stack_orchestrator/deploy/k8s/helpers.py
index ddba30bc..8b367f86 100644
--- a/stack_orchestrator/deploy/k8s/helpers.py
+++ b/stack_orchestrator/deploy/k8s/helpers.py
@@ -942,6 +942,41 @@ def envs_from_compose_file(
     return result
 
 
+def translate_sidecar_service_names(
+    envs: Mapping[str, str], sibling_service_names: List[str]
+) -> Mapping[str, str]:
+    """Translate docker-compose service names to localhost for sidecar containers.
+
+    In docker-compose, services can reference each other by name (e.g., 'db:5432').
+    In Kubernetes, when multiple containers are in the same pod (sidecars), they
+    share the same network namespace and must use 'localhost' instead.
+
+    This function replaces service name references with 'localhost' in env values.
+    """
+    import re
+
+    if not sibling_service_names:
+        return envs
+
+    result = {}
+    for env_var, env_val in envs.items():
+        if env_val is None:
+            result[env_var] = env_val
+            continue
+
+        new_val = str(env_val)
+        for service_name in sibling_service_names:
+            # Match service name followed by optional port (e.g., 'db:5432', 'db')
+            # Handle URLs like: postgres://user:pass@db:5432/dbname
+            # and simple refs like: db:5432 or just db
+            pattern = rf"\b{re.escape(service_name)}(:\d+)?\b"
+            new_val = re.sub(pattern, lambda m: f'localhost{m.group(1) or ""}', new_val)
+
+        result[env_var] = new_val
+
+    return result
+
+
 def envs_from_environment_variables_map(
     map: Mapping[str, str]
 ) -> List[client.V1EnvVar]: