Watson and partner Henri Kontinen of Finland beat Robert Farah of Colombia and Anna-Lena Groenefeld of Germany 7-6 (5), 6-4.
Murray previously won Wimbledon in 2013.
The couple asked him about his baby daughter Sophia, in an exchange caught by the BBC.
Murray also briefly spoke to British actor Benedict Cumberbatch.
The 29-year-old had already lost the Australian and French Open finals - both to Djokovic - this year, as well as last year's US Open decider, and made amends here in the finest style. His only other Grand Slam victory came in 2012, when he won the U.S. Open.
Of Murray's 10 previous slam finals, two of which came this year, three had been against Federer and seven against Novak Djokovic, but being the favourite for the first time had not given him the jitters. Murray covered 2,367 metres in the final, compared to the 2,430 metres Raonic ran.
Like Bouchard, Raonic went down in straight sets, but he put up a much better fight.
His victory against Canadian sixth seed Milos Raonic thrilled crowds who watched it on a big screen near Tower Bridge in London. "Andy has been playing great and he deserved to win, congratulations to him", he said. On his second match point at 6-2, he drove another forehand that got Raonic on the run for a backhand he netted. Murray added a seventh to the Canadian's deficit column and moved with assurance to the third set.
Andy Murray broke down in tears of joy after becoming Wimbledon champion for a second time.
The tweet read: "The Duke and Duchess of Cambridge are looking forward to attending today's Wimbledon men's final - it's been a great fortnight of tennis".
Murray leads Milos Raonic 4-3 on Centre Court.
Raonic unleashed a serve of 147mph in that game but his opponent still won the point - a dispiriting snapshot of his afternoon. His first serve percentage, he only made nine unforced errors...
Three years ago, he became the first British man to win Wimbledon since Fred Perry in 1936.
Andy Murray and Milos Raonic are on Center Court and warming up for the Wimbledon final.
Settling in Ontario, Raonic started playing tennis when he was eight, training in the morning and evenings after school while his father Dusan fed the ball machine.
Victory preserved the iron-grip on the majors of the sport's "Big Four" with Lleyton Hewitt the last man outside of Murray, Djokovic, Federer and Rafael Nadal to win Wimbledon back in 2002.
Murray also paid tribute to his family and his support team for their help in winning a third grand slam title.
The player attempting to become Canada's first grand slam singles champion was struggling at the net, either with his own volleys, or Murray's passing shots, which were superb.
Andy Murray's second finals win at Wimbledon has been a sliver of good news for a country still digesting the consequences of the Brexit vote.