diff --git a/esphome/components/packages/__init__.py b/esphome/components/packages/__init__.py
index a46783bb58..252a24061a 100644
--- a/esphome/components/packages/__init__.py
+++ b/esphome/components/packages/__init__.py
@@ -10,6 +10,7 @@ from esphome.components.substitutions import (
     ContextVars,
     push_context,
     resolve_include,
+    resolve_substitutions_block,
     substitute,
 )
 from esphome.components.substitutions.jinja import has_jinja
@@ -516,23 +517,12 @@ def do_packages_pass(
     if CONF_PACKAGES not in config:
         return config
 
-    raw_substitutions = config.pop(CONF_SUBSTITUTIONS, {})
     with cv.prepend_path(CONF_SUBSTITUTIONS):
-        if isinstance(raw_substitutions, yaml_util.IncludeFile):
-            # Resolve `substitutions: !include file.yaml` before feeding into UserDict.
-            # Seed with command-line substitutions so `!include ${var}.yaml` can
-            # reference CLI-provided vars in the filename.
-            raw_substitutions, _ = resolve_include(
-                raw_substitutions,
-                [],
-                ContextVars(command_line_substitutions or {}),
-                strict_undefined=False,
+        substitutions = UserDict(
+            resolve_substitutions_block(
+                config.pop(CONF_SUBSTITUTIONS, {}), command_line_substitutions
             )
-        if not isinstance(raw_substitutions, dict):
-            raise cv.Invalid(
-                f"Substitutions must be a key to value mapping, got {type(raw_substitutions)}"
-            )
-    substitutions = UserDict(raw_substitutions)
+        )
     processor = _PackageProcessor(
         substitutions, command_line_substitutions, skip_update
     )
diff --git a/esphome/components/substitutions/__init__.py b/esphome/components/substitutions/__init__.py
index 6f24011210..dfdf186e5a 100644
--- a/esphome/components/substitutions/__init__.py
+++ b/esphome/components/substitutions/__init__.py
@@ -414,6 +414,31 @@ def _warn_unresolved_variables(errors: ErrList) -> None:
         )
 
 
+def resolve_substitutions_block(
+    substitutions: Any,
+    command_line_substitutions: dict[str, Any] | None,
+) -> dict[str, Any]:
+    """Resolve a deferred ``substitutions: !include file.yaml`` and validate the shape.
+
+    The caller is responsible for wrapping the call in
+    ``cv.prepend_path(CONF_SUBSTITUTIONS)`` for error reporting.
+    ``command_line_substitutions`` seeds the filename context so
+    ``substitutions: !include ${var}.yaml`` can reference CLI-provided vars.
+    """
+    if isinstance(substitutions, IncludeFile):
+        substitutions, _ = resolve_include(
+            substitutions,
+            [],
+            ContextVars(command_line_substitutions or {}),
+            strict_undefined=False,
+        )
+    if not isinstance(substitutions, dict):
+        raise cv.Invalid(
+            f"Substitutions must be a key to value mapping, got {type(substitutions)}"
+        )
+    return substitutions
+
+
 def do_substitution_pass(
     config: OrderedDict, command_line_substitutions: dict[str, Any] | None = None
 ) -> OrderedDict:
@@ -429,20 +454,9 @@ def do_substitution_pass(
     # Use merge_dicts_ordered to preserve OrderedDict type for move_to_end()
     substitutions = config.pop(CONF_SUBSTITUTIONS, {})
     with cv.prepend_path(CONF_SUBSTITUTIONS):
-        if isinstance(substitutions, IncludeFile):
-            # Resolve `substitutions: !include file.yaml` before validating the shape.
-            # Seed with command-line substitutions so `!include ${var}.yaml` can
-            # reference CLI-provided vars in the filename.
-            substitutions, _ = resolve_include(
-                substitutions,
-                [],
-                ContextVars(command_line_substitutions or {}),
-                strict_undefined=False,
-            )
-        if not isinstance(substitutions, dict):
-            raise cv.Invalid(
-                f"Substitutions must be a key to value mapping, got {type(substitutions)}"
-            )
+        substitutions = resolve_substitutions_block(
+            substitutions, command_line_substitutions
+        )
         substitutions = merge_dicts_ordered(
             substitutions, command_line_substitutions or {}
         )