Delve, 32, will move to the Welsh region this summer.
It will be his first professional contract in Wales, having previously played for Bath, Gloucester and Super Rugby side the Melbourne Rebels before switching to club rugby in Japan.
The Ospreys announced that Cardiff-born Delve, who won the last of his 11 Wales caps against Italy during the 2010 Six Nations Championship, has agreed a two-year deal.
Rugby
Ospreys snatch win with late Rhys Webb double
30/04/2016 AT 15:46
"I am lucky to have played in some great places, and I've travelled the world, but this opportunity to play in Wales was too good to say no to," Delve said.
" Of all the potential moves I could have made at this point of my career, this was the one that really excited me."
Rugby
Ospreys pile on the points to stay in European Champions Cup hunt
15/04/2016 AT 21:02
Rugby
Ospreys pile on the points to stay in European Champions Cup hunt
15/04/2016 AT 21:01