Britain's royal couple, who have just returned from a hectic 19-day tour of New Zealand and Australia, had planned a low-key celebration as they spend time with baby George.
According to the 'Daily Mirror', they will be catching up with the Middletons and the rest of their family and reuniting them with baby George to show them how much he has grown.
The nine-month-old baby prince gained an "extra fat roll" on the trip, according to 32-year-old Kate, as well as a fuller head of hair.
On their anniversary last year, pregnant Kate spent the day on a solo visit to a children's hospice in Hampshire, while William was in Wales on duty as Royal Air Force (RAF) search and rescue pilot.
The Duke and Duchess of Cambridge had got married at a glittering ceremony at Westminster Abbey in London on April 29, 2011.
The event was watched by a worldwide audience of millions.
They became parents for the first time in July last year and moved into their renovated Kensington Palace apartment in the autumn.
Prince William (31) has since left his job in the military and took on an agricultural management course at Cambridge University.
Traditionally couples exchange gifts made of leather to mark their third wedding anniversary.