A washing machine appliance and additive dispensing assembly are provided herein. The washing machine appliance may include a cabinet, a wash tub, a wash basket, and an additive dispensing assembly. The additive dispensing assembly may be positioned within the cabinet and configured to provide wash fluid to the wash tub. The additive dispensing assembly may include a water supply conduit, a booster pump, an additive dispenser, and a siphon channel. The water supply conduit may extend between a water supply and the wash tub. The booster pump may be positioned along the water supply conduit downstream from the water supply. The siphon channel may extend from the additive dispenser to the water supply conduit downstream from the booster pump.
