The TV presenter, 42, was involved in a collision with two other cars while he was driving his Mini in Richmond, West London and was arrested at around 4pm after failing a roadside breathalyser test.
A Metropolitan Police spokeswoman said that he was "taken to a south London police station for questioning and has since been released under investigation."
Inquiries continue, the spokeswoman added.
Police previously confirmed that a number of individuals were treated at the scene for minor injuries, and a child passenger from one of the cars was taken to hospital to be checked as a precaution.
This is the latest in a string of personal setbacks for the star, who works as Ant and Dec with Declan Donnelly.
McPartlin entered rehab last year after struggling with an addiction to painkillers following a knee operation in 2015.
He returned to screens in November for I'm A Celebrity ... Get Me Out Of Here! and jokingly mentioned his rehab stint along with his TV partner.
In January, McPartlin confirmed that he and his wife Lisa were separating after 11 years of marriage.
At the National Television Awards a few days after the split, McPartlin referred to his "tough year" while picking up the presenting prize with Donnelly.
Following McPartlin's arrest, fans have questioned whether his weekly programme, Ant and Dec's Saturday Night Takeaway, will air as normal this weekend.
ITV has yet to comment on the programme, which is scheduled to air live on Saturday at 7pm.