Brendan Irvine qualified for his second Olympic Games after a clinical display against Istvan Szaka in London while there were also wins for Aidan Walsh and Michael Nevin.
Irish captain Irvine produced a classy performance as he claimed victory over nine-time Hungarian national champion Szaka by unanimous decision.
Boasting a superior reach and height advantage, Irvine picked off his opponent with a range of body shots and right hooks during the opening round.
Those punches to the body slowed Szaka, who was reliant on his speed to close the gap, and Irvine caught him with three powerful head shots during a one-sided second round.
Irvine continued to unleash an array of powerful shots in the final round as he claimed an impressive victory that secured his place at a second successive Olympics.
Meanwhile, Walsh and Nevin both advanced in their Olympic qualifiers in London but Belfast boxer Carly McNaul suffered a disappointing defeat.
Walsh produced a counter-attacking masterclass in his welterweight contest against Estonia's Pavel Kamanin, picking his opponent off at will while using his speed and footwork to frustrate his opponent.
The 22-year-old won by unanimous decision.
Michael Nevin followed him through, but he was given a tougher test by Dutch middleweight Max van der Pas.
Nevin started the fight well, landed some early punches in the first round. He was put under pressure in the second, but three of the judges still awarded it to him.
Van der Pas attacked in the last, knowing that he needed to put in a huge round to steal it, but Nevin showed his experience to book a place in the quarter-finals.
He's now just one win away from the Olympic Games, with Arman Darchinyan standing in his way.
It is unclear when Walsh and Nevin's next fights will take place after the IOC suspended the qualifiers until May at the earliest.
Elsewhere there was Irish disappointment earlier on Monday as McNaul lost to Charley-Sian Davison in her flyweight bout.
The British fighter looked impressive throughout as she won by unanimous decision.
McNaul, who was twice given the count in the last round, was unable to land the blows as her opponent picked her off.
The evening ended in disappointment for European champion Kurt Walker, however, who lost by unanimous decision to Germany's Hamsat Shadalov in the featherweight ranks.
Three Irish boxers progressed on Sunday at the Copper Box Arena.
