Nick Cannon tells TMZ ... when it comes to helping his former Nickelodeon co-star Amanda Bynes -- all he can do is pray.
Cannon -- who appeared on "All That" with Bynes back in the day -- has been an outspoken supporter of the actress throughout her recent issues.
But at LAX yesterday, Cannon told us it's gonna take some divine intervention to save his friend.
"She's in my prayers," Cannon told TMZ ... "I'm praying for her. That's all you can do."