France now clears a bill allowing same-sex couples to marry and adopt children too.
The bill was approved on April 23 by parliament but was immediately challenged on constitutional grounds by the opposition UMP. Its clearance would see France's first gay wedding in a matter of days.
A statement by the council, however, said that gay adoption did not automatically mean the "right to a child" and that the "interest of the child" would be the overriding factor in such cases.
The issue of gay marriage has divided France, which is officially secular but overwhelmingly Catholic, with street protests against the bill drawing hundreds of thousands that often spilled over into violence.
President Francois Hollande, who had made "marriage for all" a key election pledge, has said he will sign the bill into law once the council ruled on the challenge.