"Okay. It happened. Hugo and I just got married," O'Hare, 49, wrote on Thursday.
Their union comes days after same-sex marriage was legalized in the state of New York.
O'Hare, a Tony award winner, just played the villainous vampire Russell Edgington on True Blood. He also recurs on The Good Wife as the extremely liberal Judge Abernathy and will appear in Ryan Murphy's American Horror Story, which premieres on FX this October.