The Brit, who plays Gandalf the wizard in the series, turned up unannounced at the AMC Lincoln Square cinema in the Big Apple for the screening in the early hours of the film's first day of release last Friday (13Dec13).
When MCKellen took to the stage in front of the big screen before the movie began, the audience jumped to their feet to give him a standing ovation.
The actor told the crowd, "Congratulations on being the first audience in New York to see The Desolation of Smaug. This is where I wanted to be right now as we turn midnight on to lucky Friday the 13th.
"I've seen this movie. You're going to have a wonderful time. The dragon goes on a bit long, but by golly, looks fierce."
MCKellen is currently residing in New York City while appearing on Broadway in a double bill of Harold Pinter's No Man's Land and Samuel Beckett's Waiting for Godot alongside Sir Patrick Stewart.