The veteran striker links up with former Bournemouth team-mate Carl Fletcher, who is now Argyle manager, at Home Park.
Fletcher has struggled to break into the Cherries' first team in recent weeks, and has not featured for the Dorset side since the 1-0 defeat to Rochdale on February 18. The 39-year-old is unlikely to make his Plymouth debut at Northampton this weekend, however, as he continues to recover from a thigh injury.
Carl Fletcher told the Pilgrims' official website: "I know Steve, I've played with him and I know what he can bring. He's been in this situation before with Bournemouth. Big target men are hard to find in football, let alone in this division, and he's one of the best.
"I know he's Bournemouth through and through and that he'd love to be playing there week in, week out but the situation is that we're lucky enough to get him.
"It's something that we've been working on for a few weeks now so I'm delighted that I've managed to persuade him to come down and be involved and help us."