One of the Cambridge rowers almost fell out of his boat and lost control of his oar as the two crews clashed in the early stages.
The incident allowed Oxford to surge forward and build up a comfortable lead.
The BNY Mellon Boat Race was watched by crowds along the banks of the Tideway, between Putney and Mortlake in west London.
Oxford has now cut Cambridge's overall lead to 81-78 in the series between the two famous rivals, with just the one tied affair still in the overall standings.
The winners came at a time of 18 minutes and 36 seconds.
The universities first raced in 1829, and the Boat Race is one of the oldest sporting events in the world.
Oxford rower Karl Hudspith described the incident that crushed Cambridge's hopes of a win as "very unfortunate".
"It's a really awful way to end a whole year of training," he told the BBC.
He added: "I think we showed after the incident that we kept on pulling away. We put quite a big margin into them in the end.
"I think we were the better crew and that did show in some of our previous fixtures as well. Like I said, it's just unfortunate it had to end that way."
Reflecting on the incident, Cambridge's Steve Dudek said it was a "very, very difficult way to lose", but added: "That's the nature of the Boat Race."
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