In an expletive-laden speech inside the ring, Joshua praised Usyk for fighting so well in the circumstances.
Usyk also claimed the Ring Magazine belt with the win. There's only one heavyweight title that Usyk doesn't own — the WBC one that was vacated this year by Tyson Fury, who says he is retired.
When asked about Fury, Usyk said: "I am sure Tyson Fury is not retired yet. I am sure Tyson Fury wants to fight me. If I'm not fighting Tyson Fury, I'm not fighting at all."
Two judges gave it to Usyk, one 115-113 and the other 116-112. The other gave the fight to Joshua, 115-113.
Joshua, a two-time heavyweight champion, fell to his third loss in 27 fights and his career is at a crossroads.
Where Usyk goes from now appears to depend on Fury.