The trio have a one-shot lead over Mark Whelan (Castlewarden Golf & CC), with Jerry Scullion (Kilkeel GC) back in fourth on four under.
“I have been playing well recently and I knew something was going to happen,” said Kilpatrick, who went bogey-free in his six-birdie round.
“I finished the recent Pro-Am at Carne with a 66 and that gave me some added confidence coming down here. I just continued doing the same things.
“I really felt that today was a good day to make a score. The course is playing firm, it wasn’t very windy and it was generous.”
Moriarty and Rice also signed for bogey-free rounds on a day when 26 players matched or bettered par around the Twin Oaks course.
“I haven’t played an awful lot this season and I feel like I am only coming into some sharpness now. I played nicely and game myself a lot of chances today,” said Moriarty, 38.
Rice, who missed last year’s championship, is still getting to grips with the layout after carding a two-over-par 74 in Wednesday’s pre-tournament pro-am.
He said: “I’m happy enough with that. It was tricky at times because of the cross wind but it was pleasing to start with that score today.”
Defending champion Damien McGrane opened his campaign with a two-under-par round of 70 and was joined on that mark by David Higgins (Waterville GC), Simon Thornton (Simon Thornton Golf), Shane Jenkinson (St Margaret’s Golf & Country C), Adam Dunmore (Bundoran GC), and Michael McGeady (Seamus Duffy Golf Academy).
“It’s a steady start and I’m exactly where I want to be,” said McGrane.
“I played steadily from start to finish, holed a few putts and missed a few but I played the par threes poorly today.”
The second round of the 107th Irish PGA Championshipgets under way at 8am today.