A convertible cargo case for a wagon is provided. The cargo case has a housing having a first side wall, a second side wall opposing the first side wall, a third side wall joining the first side wall and the second side wall, a fourth side wall opposing the third side wall and joining the first side wall and the second side wall, and a bottom wall joining a bottom end of the first side wall, second side wall, third side wall and fourth side wall to define a cavity. A connector extends from the cavity. The connector has a receiver for removably securing the housing to the wagon, wherein the housing is convertible between three configurations: an open cargo configuration, a closed cargo configuration, and a wagon storage configuration.