Seal appeared to address Winfrey directly in his accompanying caption.
"Oh I forgot, that's right ... you'd heard the rumours but you had no idea he was actually serially assaulting young starry-eyed actresses who in turn had no idea what they were getting into. My bad. #SanctimoniousHollywood," he wrote.
Seal's social media followers flooded the post with comments — many of them negative.
"Your job is to sing Kiss From A Rose. Do that and be quiet," wrote one.
"Pretty gauche to blame women for the crimes of men," said another.
Others asked why Seal didn't turn his attention to ex-wife Heidi Klum, who enjoyed a long professional relationship with Weinstein (The Weinstein Company was executive producer of her show Project Runway).
"Sooooo, are you going to post Heidi's picture too being that she was friends with him as well ... Or is your outrage selective?" wrote one.
"So when are you going to post about Heidi Klum? She was super close with that man," said another.
Seal has met Winfrey before — he and Klum appeared on a 2007 episode of The Oprah Winfrey Show, telling the talk show queen about their relationship during a joint interview.
The Voice Australia coach is no stranger to controversy — last year he angered viewers of the Channel 9 singing show by declaring Lorde's critically acclaimed hit single Green Light was a "bad song".