The expectant princess, 30, wore a green floor-length dress with a daring thigh-high slit as the guest of honor at the BBC Sports Personality of the Year awards show in London.
"We're so delighted to be joined by Her Royal Highness the Duchess of Cambridge," host Gary Lineker told the audience at the ExCeL arena.
As the crowd of thousands applauded, Kate beamed a wide smile and marched out clutching the lifetime achievement trophy for Sebastian Coe, who led the London 2012 Olympics, before appearing to share some warm congratulatory words with him.
She remained on the stage to hand over another award, the top prize for sports personality, which went to cyclist Bradley Wiggins. As Wiggins soaked up the applause, Kate took a chance to chat with runner-up athlete Jessica Ennis.
Kate wasn't at the arena for the entire four-hour event. She arrived at around 9:30 p.m. for the last hour.
Kate, who left the hospital on Dec. 6 after treatment for severe morning sickness, was an ambassador for the British Olympic and Paralympics teams, and was only announced as one of the prize givers a few hours before the ceremony.