The practical car seat won the Mother & Baby award for Best Baby in the infant car seat category in 2012.
European Managing Director of Britax, Ian Watson, said the company were "delighted and honoured" that the royal couple decided to purchase one for their new arrival.
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"As a British brand the leader in child travel safety, we are delighted and honoured to hear that the Prince of Cambridge could be making his first journey in one of our infant carriers," he said.
"We send our warmest wishes of health and happiness to TRH The Duke and Duchess of Cambridge as they begin their exciting journey in to parenthood."
The website offers more details on the car seat. "The lightweight Baby-Safe provides a secure travel solution for your bay from birth," it reads.
"The integral cushion allows your baby to lie in a more natural comfortable position."
The car seat can be used to transport the royal baby for at least one year, but the brand also have a model called the King Plus, for babies over nine months old.
Onlookers first got a glimpse of the car seat when one of the couple's aids was spotted carrying it into the hospital.
William and Kate emerged from the Lindo Wing several hours later, with Kate cradling Prince of Cambridge in her arms.