A dishwasher may include a tub at least partially defining a treating chamber, an airflow conduit, and a blower assembly fluidly coupled to the airflow conduit. The blower assembly may include a first impeller effecting a flow of ambient air to the treating chamber and a second impeller effecting a flow of mixed air from the treating chamber exhausting the mixed air from the treating chamber. Additionally, at least one of the first and second impellers may effect a flow of ambient air that bypasses the tub and combines with the mixed air before being exhausted from the dishwasher.