Pitt raises six children - Maddox, nine; Pax, seven; Zahara, six; Shiloh, five; and two-year-old twins Knox and Vivienne - with partner Angelina Jolie.
"It is encouraging that New York has joined the movement to grant equal marriage rights to its citizens. But it is each American's Constitutional right to marry the person they love, no matter what state they inhabit," contactmusic.com quoted the 47-year-old actor as saying.
"No state should decide who can marry and who cannot. Thanks to the tireless work of so many, someday soon this discrimination will end and every American will be able to enjoy their equal right to marriage," he added.