An advisor to Queen Elizabeth II approved the coat of arms, which includes acorns to symbolize strength and continuity. There are three acorns - one to represent each of the Middleton children.
It also includes chevrons that represent hills and mountains in a reference to the outdoor activities the family enjoys.
The gold color of the chevron refers to Kate Middleton's mother Carole Middleton, whose maiden name was Goldsmith.
Officials say the bride's parents helped design the new coat of arms.
After the royal wedding, Kate Middleton will place her family's coat of arms next to those of Prince William.
The wedding program will feature the new coat of arms on the back cover and will be sold to crowds lining the route of the royal wedding procession on April 29.