Mr. Christie, a Republican, waited until the last possible minute to make his decision on the bill. If he had not signed or vetoed it by Monday, it would have gone into law automatically.
Before the Legislature approved the bill by a wide margin this summer, Mr. Christie had said he was “of two minds” on it: he believes that parents should be left alone to decide how to raise their children, but, as a spokesman later clarified, he does not believe in so-called conversion therapy, which claims to “cure” gays and lesbians, in some cases by forcing them to masturbate to images of the opposite sex.
The governor has all but declared his intention to run for president in 2016, and had to be mindful of conservative primary-state voters who would see the bill as government intrusion into child-rearing.
But the therapy has lost significant support in recent years, as leading scientific and medical groups have disputed the idea that sexual orientation can be changed, and argued that the therapy can cause, in the words of the American Psychiatric Association, “depression, anxiety and self-destructive behavior.” In June, Exodus International, a Christian group that was a leading proponent of conversion therapy, disbanded after 37 years, apologizing to gays and lesbians for the harm it had caused.
In a statement accompanying his signature on the bill, Mr. Christie said, “I still have those concerns” — about intruding onto parents’ rights.
“However,” he added, “I also believe that on issues of medical treatment for children we must look to experts in the field to determine the relative risks and rewards.”
Gay rights advocates said they hoped that signing the bill signaled an “evolution” for the governor, a Roman Catholic who last year vetoed legislation that would have allowed same-sex marriage.
“I hope that the governor, in saying that he believes that New Jersey’s youth deserve protection, means that he sees that the next step in that evolution is to allow those same youth the dignity of marriage in their future,” said Troy Stevenson, the executive director of Garden State Equality, the state’s leading gay rights group. “To say that someday they will be fully included in society instead of being relegated to second-class citizenship, as they are now.”
But the governor does not evolve easily. He has strongly counseled Republican legislators from supporting an attempt to override his veto on same-sex marriage. He has said that he would abide by the results of a referendum approving same-sex marriage, but advocates say putting the issue on the ballot would invite national groups to campaign against it — and defeat it, as they have in most states.
Mr. Christie was not eager to talk about the bill in an appearance with Hispanic business leaders here in northern New Jersey. As reporters asked him his plans for the bill, he ignored their questions, continuing to smile for snapshots with voters.
California banned conversion therapy for minors last year, though a legal challenge is pending, and the Massachusetts legislature is considering a similar ban.