A modular circuit breaker includes a module assembly coupled to a primary assembly. The primary assembly includes a primary housing, separable contacts disposed therein, a first terminal conductor electrically connected to one of the separable contacts, a conductive tab electrically connected to another one of the separable contacts and which extends outward from a first end of the primary housing, an operating mechanism disposed in the primary housing for selectively opening and closing the separable contacts, and a trip mechanism disposed in the primary housing cooperative with the operating mechanism to trip open the separable contacts. The module assembly includes a module housing having a second terminal conductor positioned therein and electrically connected to the conductive tab, a third terminal conductor structured to be electrically connected to a neutral conductor of a load, and a fourth terminal conductor structured to be coupled to a neutral bus.