The presenter, who hosted all 11 series of the show on Channel 4, said that the Ultimate Big Brother housemate was the perfect choice to replace her.
McCall told the Daily Star: "Brian is a natural choice as the new host and will be a very popular one, I'm sure.
"He has buckets of personality and tons of TV experience. I know he'll be a real laugh and very watchable - I'm backing him all the way!"
Dowling has previously stated that he hopes people won't compare him to McCall, adding that he is a "huge fan" of hers.
McCall has since gone on to host The Biggest Loser and will return for a second primetime series next year.
More on the new series of Big Brother on Channel 5:
> Big Brother new eye logo revealed by Channel 5
> Is Brian Dowling the right choice for Big Brother? - Poll
> New Big Brother host Brian Dowling: Career in pictures
> Big Brother to be hosted by Brian Dowling and Emma Willis, confirms Channel 5
Watch the new trailer for Big Brother on Channel 5 below: