A brace from forward Robbie Keane helped Giovanni Trapattoni's side to a comfortable win in Dublin.
Northern Ireland held out early on but were forced to play the majority of the second half with 10 men after teenage defender Adam Thompson was sent off.
Wolverhampton attacker Stephen Ward scored on his international debut, slotting from close range to make it 1-0 after Northern Ireland goalkeeper Alan Blayney spilled a Keith Treacy cross.
Keane doubled their advantage on 37 minutes after another dreadful error.
Northern Ireland full-back Lee Hodson failed to put enough power on his back pass to Blayney, allowing Keane to intercept and delicately chip the advancing goalkeeper.
The hosts made it three just prior to the break, as a brilliant team move led to an own goal from defender Craig Cathcart.
Blayney initially saved a cutback from Seamus Coleman after a tidy passing exchange, only to palm his save into the legs of Cathcart and watch the ball deflect into an empty net.
Keane completed his double on 54 minutes, converting from the penalty spot after 18-year-old Thompson was shown a straight red card for bringing him down when he was through on goal.
West Bromwich Albion attacker Simon Cox completed the scoring 10 minutes from the end as he too scored on debut, placing into the bottom corner after the Northern Irish defence allowed him space on the edge of the area.