In his first fight since his British featherweight title defeat to Ryan Walsh in May, McCullough was matched with the much-larger Josh Baillie.
The English away fighter had upset previous, but was put away in the third of six rounds by a fresh-looking McCullough.
A calm and collected McCullough began well, looking to set up body shots as the boxers felt each other out.
The Shankill fighter showed his power in the second as a long left hook stumbled Baillie to the ropes. McCullough was looking assured and punching with intent as the fight began to warm up.
It was all over then n the third round, with a chopping right from McCullough sending the visitor down heavily. Baillie rose, but was on unsteady legs and the bout was waved off to give McCullough an impressive comeback win
McCullough’s record now reads 18(11)-4(3) as he looks to get back in the domestic mix, while the outgunned Baillie drops to 5(2)-4(1).