diff --git a/esphome/components/rp2040/generate_boards.py b/esphome/components/rp2040/generate_boards.py
index 63df8d4252..8aaab119ac 100644
--- a/esphome/components/rp2040/generate_boards.py
+++ b/esphome/components/rp2040/generate_boards.py
@@ -120,7 +120,7 @@ def _get_variant(json_file: Path) -> str | None:
     """Get variant name from a board JSON file."""
     if not json_file.exists():
         return None
-    with open(json_file) as f:
+    with open(json_file, encoding="utf-8") as f:
         data = json.load(f)
     return data.get("build", {}).get("variant")