He was up against Seychelles' Andrique Allisop
David Oliver Joyce has advanced to the last-16 in the Men's lightweight competition in Rio.
On his Olympic debut, the Athy boxer was in control throughout against Andrique Allisop of the Seychelles in the first round bout.
The victory was awarded by unanimous decision.
Joyce faces Albert Selimov of Azerbaijan next for a place in the quarter-finals.
It was Ireland's second win in the ring today as Ballymena's Steven Donnelly advanced to the welterweight last 16 earlier after comfortably coming through his preliminary round fight against Algerian opponent Zohir Kedache.