An aft frame for a transition duct of a gas turbine combustor includes a main body having an outer rail, an inner rail, a first side rail circumferentially separated from an opposing second side rail, a forward portion, an aft portion and an outer surface. An inlet port extends through the outer surface and an exhaust port extends through the forward portion. A serpentine cooling passage is defined within the main body beneath the outer surface. The serpentine cooling passage is in fluid communication with the inlet port and the exhaust port. A conduit may be connected to the exhaust port for routing a compressed working fluid away from aft frame.