Us Weekly reports that the actress was picking up the 'Female Star of the Year' honour at the ShoWest awards in Las Vegas.
The strap on Heigl's red dress broke while she was giving her speech, but Access Hollywood host Billy Bush rushed over to hold up the fabric.
Bush later wrote on Twitter: "Oh my. Hosting showest awards in LV. Heigl comes up to get award, dress strap breaks... I hold her top on while she accepts!"
Heigl managed to finish her speech and later found a pin backstage to keep her outfit together.
Earlier, ShoWest director Robert Sunshine had explained that Heigl won the award for her "ever-present charm and innate talent", adding: "Her comedic timing and flair for acting are showcased in each of her roles and have captivated audiences around the globe."
Heigl was reportedly released from her Grey's Anatomy contract earlier this month.