diff --git a/esphome/components/number/__init__.py b/esphome/components/number/__init__.py
index 230c3aa0c1..ac0329fcc6 100644
--- a/esphome/components/number/__init__.py
+++ b/esphome/components/number/__init__.py
@@ -252,7 +252,10 @@ async def setup_number_core_(
     cg.add(var.traits.set_max_value(max_value))
     cg.add(var.traits.set_step(step))
 
-    cg.add(var.traits.set_mode(config[CONF_MODE]))
+    # Only set if non-default to avoid bloating setup() function
+    # (mode_ is initialized to NUMBER_MODE_AUTO in the header)
+    if config[CONF_MODE] != NumberMode.NUMBER_MODE_AUTO:
+        cg.add(var.traits.set_mode(config[CONF_MODE]))
 
     for conf in config.get(CONF_ON_VALUE, []):
         trigger = cg.new_Pvariable(conf[CONF_TRIGGER_ID], var)