A spokeswoman for the couple said: 'I can confirm Zara is pregnant with her second child'.
Zara married Tindall in 2011 and welcomed a daughter Mia, who is 17th in line to the throne, in January 2014.
Buckingham Palace said overnight the queen and the royal family are "very pleased' with the news".
She was due to give birth is due to around Spring 2017 but she is believed at have miscarried.
This newest addition will become The Queen and Duke of Edinburgh's seventh great-grandchild, and Princess Anne's fourth grandchild.
The Last Jedi (Already) Set to Pass $1 Billion at Box Office
The $4.06 billion also does not count the more lucrative marketing strategy Walt Disney Studios makes out of the Star Wars films. Of course, this amount does not even count the fact that Star Wars: The Last Jedi has yet to air in China on Jan 5.
It's shaping up to be a massive year for the British royal family, with not only a massive wedding to look forward to, but the arrival of two babies.
The couple's outing winter getaway came a year after they announced, via a spokesperson, that Zara had tragically suffered a miscarriage. A royal spokeswoman made the announcement on Christmas Eve.
He said: 'One thing you do learn is how many other people have had to go through the same. "The saving grace for us has been Mia, our daughter who is now 3", he told The Sunday Times back in May. However down we feel she will come running up in our faces.
Little Mia is known for stealing the show - from posing with her great-grandmother the Queen's handbag during an official photo, to getting kisses from Zara's cousin Prince Harry at polo events.