Hickie will miss November appointments with New Zealand, Australia and Romania after dislocating his right fibula.
The 29-year-old was hurt during a training session as Leinster prepared for next Saturday's European Cup opener against Bath in Dublin.
Hickie underwent surgery on Monday night, and is now recovering at home, but he has been ruled out of Leinster's first two European Cup games, plus the autumn Tests.
It is the latest setback to affect Ireland coach Eddie O'Sullivan, who has already lost captain Brian O'Driscoll from the November programme because of a dislocated shoulder suffered on Lions duty in New Zealand this summer.
Elsewhere, lock Paul O'Connell (broken thumb) and scrum-half Peter Stringer (knee) are racing against time to be fit for the November 12 All Blacks clash at Lansdowne Road.