An exhaust brake is incorporated with an internal combustion engine. The brake comprises an exhaust rocker arm actuated by an exhaust cam for operating an exhaust valve; a brake rocker arm actuated by a brake cam; a first contacting unit held by either one of the exhaust and brake rocker arms; a second contacting unit held by the other of the exhaust and brake rocker arms. The second contacting unit is contactable with the first contacting unit when an exhaust braking is needed. Only when the brake rocker arm is actuated by the brake cam upon need of the exhaust braking, there induces the contact between the second and first contacting units, which provides an integral action of the exhaust and brake rocker arms thereby to actuate the exhaust valve for establishing the exhaust braking.