The 23-year-old was knocked unconscious on 14 minutes as he dived over the line to score a try against the reigning United Rugby Championship winners. Opposite man Shane Daly was making the cover tackle to prevent the try, and was subsequently yellow carded.
McIlroy was treated at Royal Victoria Hospital Emergency Department, where he was discharged later that evening.
Ulster have not given a timescale as to how long the fullback will be out of action for, with fixtures against the Lions, Glasgow Warriors and Edinburgh coming in the next three weeks before the Champions Cup begins.
Dan McFarland’s side went on to win 21-14, leaving Ulster in fourth place in the URC standings.
“I was pleased with a lot of what we did,” McFarland said to the Ulster website after the match.
“We showed real attacking intent, we were dangerous for long periods of the first half but we found ourselves at 0-14 down, on the back of their scrum getting control of us and some inaccuracy.
“They are the unbeaten champions, to come back from that is a pretty big ask with the quality Munster have. I was really proud of some of the rugby we played, it would have been nice when we got 7 points up we showed some more composure, but maybe the guys wanted to show their fighting spirit for the remaining five minutes of the game! They certainly showed that, it’s a credit to Munster that they will never say die. Munster battered away at the end and it took every ounce to stop them.”