Capped at Wales U20s and Sevens level, like Aled Thomas who was announced as joining Gloucester earlier this week, Isaacs was a member of the Wales side that won the 2009 Sevens World Cup.
He has been a regular in the Ospreys line up over the past few seasons, making in excess of 60 first team appearances.
Announcing the signing, Gloucester's Director of Rugby Nigel Davies confirmed that Isaacs has become a powerful presence in the Ospreys side and will add an extra dimension to Gloucester's midfield options.
"He started as a nine, but has been developed as an outside centre more recently. If anyone has seen him play for the Ospreys, they will realise how powerful and elusive a runner he is.
"He's a very difficult guy to stop, really hits some hard lines, breaks tackles and is a big hitter defensively. I know speaking to a lot of the players down at the Ospreys that they rate him very highly.
"Having watched him play for a long time, I have a lot of faith that he'll come and make a big impact and really put pressure on the incumbents.
"That's very important when we look at players to bring in, that they come in and help raise the bar for everybody. I'm sure Tom will come and do that. He'll bring something slightly different to what we've already got."
Isaacs' signing follows the news this week that Aled Thomas and Mark Atkinson will be joining Gloucester for next season. Previously announced already this season are the likes of John Afoa, Mariano Galarza, Richard Hibbard and Greig Laidlaw.
With more signings still to be announced this week, the rebuilding work at Kingsholm continues apace.