Opponents of the measure have vowed to sue to block the ban before it takes effect this summer.
Hutchinson vetoed the bill after pleas from doctors, social workers and the parents of transgender youths, who said the measure would harm a community already at risk for depression and suicide.
The ban was opposed by several medical and child welfare groups, including the American Academy of Pediatrics.
The measure’s sponsor referred to the procedures as experimentation and compared the restriction to other limits the state places on minors.
“They need to get to be 18 before they make those decisions,” Republican Representative Robin Lundstrum said.
Hutchinson said the measure went too far in interfering with parents and physicians, and noted that it will cut off care for transgender youth receiving treatment. He said he would have signed the bill if it had focused only on gender-confirming surgery, which isn’t performed on minors in the state.
The law will take effect in late July at the earliest. The American Civil Liberties Union said it planned to challenge the measure before then.
“This is a sad day for Arkansas, but this fight is not over — and we’re in it for the long haul,” said Holly Dickson, the executive director of ACLU Arkansas.
The override passed easily in both chambers, with the House voting 72-25 in favor and the Senate 25-8.