French striker Oumare Tounkara hit the winner after 81 minutes of Saturday’s League One clash at Boundary Park, with his second goal since joining the Latics on loan from Sunderland.
Oldham carved out two early chances as Reuben Hazell headed wide and Tounkare shot too close to keeper Shwan Jalal from 12-yards.
Winger Chris Taylor was also denied but it was Bournemouth who went in front just before half time when Rhoys Wiggins hit a free-kick from near the right touchline and watched it sail all the way into the far corner.
Oldham could have levelled on 52 minutes with former Bournemouth striker Warren Feeney blazing over from close range.
But the visitors soon went desperately close to doubling their lead as Marc Pugh’s free-kick cannoned against the post.
Oldham capitalised on the let off by scoring in the 78th minute, with Feeney’s knockdown picking out Kieran Lee to bundle home from eight yards.
And the comeback was complete after Paul Black crossed from the left and Tounkara slid in for a close-range finish.