An aftertreatment system for an engine is provided. The aftertreatment system includes a housing member having a bottom end and a top end. The housing member includes an inlet chamber and an outlet chamber defined adjacent to the bottom end and the top end, respectively. The inlet chamber is configured to receive exhaust gas via an inlet port which is coupled to an exhaust conduit of the engine to receive exhaust gas. The outlet chamber is configured to discharge the exhaust gas via an outlet port which is coupled to an exhaust pipe to discharge exhaust gas. The housing member also includes a catalytic chamber disposed between the inlet chamber and the outlet chamber. The aftertreatment system includes one or more catalyst carrying members disposed within the catalytic chamber. The one or more catalyst carrying members are configured to communicate with the inlet chamber to receive exhaust gas therethrough.