"It’s a real blow for Mark to have to pull out of this year’s race as we thought he had a great chance of being successful," British Cycling technical director Shane Sutton said in a statement.
"Unfortunately the injury he sustained during last week’s Tour of Britain is more serious than we had hoped. We wish him well in his recovery."
Adam Yates had been added to the squad following Geraint Thomas's withdrawal earlier this week, British Cycling added.
In 2011 in Copenhagen, Cavendish became the first Briton to win the road cycling road race at the world championships since the late Tom Simpson in 1965.
The road cycling world championships start in Richmond, Virginia, on Monday morning AEST with the women's and men's team time trials.