She crashed during a practice run over the weekend, injuring her knee and thumb.
Her departure was announced hours after former Girls Aloud member Sarah Harding left the reality show because of a ligament injury.
Channel 4 launched an urgent safety review earlier this month in light of the number of injured contestants.
The broadcasting regulator Ofcom has also received a number of complaints about the show and is said to be considering a formal investigation.
Other celebrities to have pulled out include Olympic gymnast Beth Tweddle, actress Tina Hobley, and Made In Chelsea's Mark-Francis Vandelli.
Linford Christie and Olympic swimmer Rebecca Adlington have also left the programme.
EastEnders actor Joe Swash chipped a bone in his shoulder, but decided to proceed with the show despite his injury. However, he was eliminated last weekend.
Mills - who is the former wife of Sir Paul McCartney - was brought in to fill one of the vacancies created by the departure of injured contestants.
Eddie "The Eagle" Edwards said earlier this month that the contestants who have had to pull out "must bear the brunt of the blame" for their injuries.
"They signed up for this, they're being paid for this. If they are hurting, it can often be self-inflicted," he said.
The current season of The Jump began on 31 January and is due to conclude this weekend, with The Wanted's Tom Parker, socialite Tamara Beckwith, actor Sid Owen, rugby player Ben Cohen and singer Dean Cain competing to be crowned the winner.
Heather Mills has become the seventh celebrity to pull out of Channel 4's The Jump due to injury.