She will present the main award and lifetime achievement honour (rumoured to be Lord Coe) when Britain's top sports stars gather to celebrate a year of sporting achievement hailed as the nation's greatest ever.
The Duchess has not been seen in public since leaving the King Edward VII's Hospital in London on December 6.
She had received three days of treatment for a condition known as hyperemesis gravidarum, which leaves expectant mothers so ill they cannot keep food or liquids down.
Kate will attend the show in her role as an official ambassador of Britain's Olympic and Paralympic team, St James' Palace said.
A spokesman said: "The Duchess of Cambridge will tonight attend the BBC's Sports Personality of the Year awards at the ExCeL London, where Her Royal Highness will present the lifetime achievement and the main sports personality of the year awards.
Former football star Gary Lineker may be the stra presenter but footballers will otherwise be thin on the ground with none in the top twelve contenders for the main award.