The Grammy nominee, 26, joined the NHL star, 29, on the carpet at the annual Bell Sens Soiree, a fundraiser for the Sens Foundation, the charity of his hockey team, the Ottawa Senators. The "Carnaval Mystique"-themed party raised $325,000 for children's healthcare.
The event kicked off a busy week for Underwood, who will be attending the Grammys on Sunday in Los Angeles, where she is up for two awards, including best female country vocal performance.
Underwood will also take part in a 3-D tribute to Michael Jackson.
The country star recently blogged on her Web site, "I am so honored and thrilled that I was asked to be a part of that! … it's going to be amazing ...a great moment in the show and one for the books!"