The former Southern United captain’s move to the League of Ireland first division (second tier) club was confirmed yesterday.
O’Keeffe (27) left Dunedin in July after four years with Southern United and Football South.
After returning to his native Ireland, he signed with Newry City, a Northern Irish championship club.
However, he only played one competitive game as the league was put on hold due to not being granted elite status.
That has led him to Galway, where coach John Caulfield said the team was looking to bring in experience.
He provides versatility, capable of playing both in the defensive line and the midfield, although was most prominently used at right back for Southern.
"I’m delighted to sign for Galway United," O’Keeffe said in a press release.
"Once I had a chat with John and listened to his vision for the club, it was a no-brainer. I came back home looking for fulltime football and this is the ideal environment for me.
"It’s about getting involved in the right setup and when you look at the facilities here, Galway United should be in the premier division, and that’s the plan for next season, to get the club back where it belongs.
"John is a manager with a proven track record. I’m 27 now, I want to win trophies. Obviously, trying to win the first division is the main objective next year. The prospect of trying to kick this club on is the really attractive part of signing for Galway United."
