That broke the record previously held by his long-time Munster and Ireland cohort Ronan O'Gara who hung up his boots at the end of last season.
And O'Callaghan, who has 94 caps for his country and went on two British & Irish Lions tours, paid tribute to the only club he has ever played for.
"When I made my debut I came on with my brother, so Munster means everything to me and to my family. I think Munster's in my DNA," he said.
"I've taken on the values and I think I've brought it into my life a bit more. I am huge thankful, I honestly am. I get to to go out with a group of lads that I love and a team that means everything to me.
"I thought I had annoyed enough people over the years, but I'm playing for a team I love in front of your family and you look at the crowd and it's the same faces that you'd have seen 15 or 16 years ago.
"You just kind of feel a tight bond around the place and that's special for me. I'm blessed to be able to play for a team that I care so much about and other people do too."