The actress/singer is headlining a week of concerts from 14-20 April (13) at Manhattan nightclub 54 Below, not far from where Hanks is performing in Broadway show Lucky Guy.
The Big star took the time to see Wilson launch her engagement, and he made his presence in the audience felt.
According to the New York Post's gossip column Page Six, Wilson performed Will You Still Love Me Tomorrow and at the end of the song, Hanks yelled out, "Yes!"
Wilson also gave a shout-out to her husband from the stage - before singing Baby, I'm Yours she admitted the track reminded her of her first kiss and quipped, "No offence, honey!"
Director Mike Nichols, actor Edward Burns and former supermodel Christy Turlington were also in the crowd.