He is the latest top player to join the Welsh All Blacks and he will join an impressive, balanced second-row pool that includes Player of the Year Euros Evans, the fast-emerging Haydn Pugh and the experienced Neil Edwards.
Director of Rugby Patrick Horgan said, "We needed an additional lock as last year, when Haydn Pugh was injured, Euros and Neil ended up playing virtually every game. They did very well for us and were excellent in the Cup Final win over Llanelli.
"But depth is going to be even more important this year especially with the extra challenge of the British & Irish Cup. Mike's athleticism makes him an ideal player in the Neath mould and, with hard work, the rewards will come his way."
Neath chairman Geraint Hawkes said, "We have tracked Mike Collins since his Maesteg days but he signed for The Ospreys who allocated him to Swansea. His career has stalled a bit since then but he is hungry for success and we believe that he has the ability, the quality and the skills to make a big impression at The Gnoll."
Mike Collins added: "I felt signing for Neath was a great opportunity for my personal development especially with the implementation of the British and Irish Cup.
"I'm looking forward to playing a competitive level of rugby at a historic club with a professional setup and a good squad of players. Neath have been a driving force over the last few years and I look forward to being part of their setup for the 2009/10 season campaign."