The competition began on 19 September 2009 with the first Round and ended on 8 May 2010 with the final.

This season they reached the quarter-finals, but were defeated by Portadown.

Linfield went on to lift their 40th Irish Cup, and fourth in five years, beating Portadown 2–1 in the final.

Portadown earned a place in the first qualifying round of the 2010–11 UEFA Europa League because Linfield had already qualified for the UEFA Champions League via the 2009–10 IFA Premiership.

Bye: 1st Bangor Old Boys, Albert Foundry, Ards Rangers, Ballymacash Rangers, Banbridge Rangers, Brantwood, Broomhedge, Crumlin United, Dollingstown, Draperstown Celtic, Dromara Village, Dungiven Celtic, Dunmurry Rec., Fivemiletown United, Grove United, Holywood, Killyleagh Youth, Magherafelt Sky Blues, Mosside, Newbuildings United, Omagh United, Raceview, Rathfriland Rangers, Richhill, Saintfield United, Seagoe, Shorts, Sirocco Works, Tandragee Rovers, U.U.J, Warrenpoint Town The matches were played on 24 and 31 October 2009.