The Queen's granddaughter will lend her name to the game Howrse and give players advice and tips on how to look after their virtual horses.
The experienced equestrian will act as a guiding voice to new player, will narrate tutorials and provide feedback.
"It's great to be involved with a game that lets children and adults alike interact with horses, horse breeding and stable management on a daily basis, meeting like-minded enthusiasts through the game's social features and sharing experiences," the blonde royal said.
"Not everyone has access to ride or care for horses regularly and Howrse provides a great opportunity to really understand more about how horses are raised and bred in an easy-to-access and fun way.
The mum-to-be, whose first baby is due this month, is understood to have been paid a six-figure sum by Ubisoft.
The Olympic silver medallist's words of wisdom will most likely feature in speech bubbles next to her picture. A spokesman confirmed that her voice would not be part of the game which has 50 million players worldwide.
Players will be able to virtually 'own' some of the 32-year-old's own horses including Olympic steed High Kingdom.
The event rider, who won a team silver at London 2012, will feature in advertising campaigns for the game as part of her deal.
Zara followed in her parents Princess Anne and Captain Mark Phillips by becoming a successful horse rider.
She won individual and team gold medals at the 2005 European Eventing Championships in Blenheim helped defend the team title again in 2007.
She missed out on the Beijing and Athens Olympics because her horse Toytown sustained injuries in training.
The former BBC Sports Personality of the Year was presented her silver medal at London 2012 by her mother.