Jordan Rhodes' last-minute winner secured a sixth win in nine games for Sheffield Wednesday as Bournemouth lost their fourth Championship game in succession.
Callum Paterson gave the Owls a deserved first-half lead when he pounced on a poor Jack Stacey pass across the penalty area and his weak stab goalwards somehow crept under Asmir Begovic.
But Bournemouth were much improved in the second half and Junior Stanislas levelled from the penalty spot after Sam Surridge was brought down by Sam Hutchinson.
But with the hosts chasing a winner, Wednesday hit them on the break as Rhodes headed home Kadeem Harris' cross from the right at the far post.