The fly-half arrived in Wales in 2014, and has become an integral member of the Cardiff Blues squad, making 43 appearances, in which he has scored 337 points.
Anscombe, who was named in Wales’ summer tour squad earlier this week, made his international debut against Ireland in 2015, and has gone on to win nine caps.
Warren Gatland said: “It is great to see Gareth re-signing his National Dual Contract and becoming another player to commit his future to the game in Wales.
“Gareth has recovered well from recent injuries to hit form once again and is deserving of his place in Wales’ upcoming summer tour.”
Speaking of the decision, Anscombe said: “It’s pleasing to recommit to Wales and Cardiff Blues, who are a region I very much want to be a part of.
“I’m looking forward to the summer tour but I’m only at the start of my international career and hopefully I can contribute a lot more in the years to come.
“There’s a lot more to do before that and it’s very important for me that Cardiff Blues finish the season well and next year to push into to the top six and play at a consistent high level.
“We’ve shown glimpses of our potential this season and are building a squad which is capable of getting there.
“The last few weeks have gone well both for the team and myself. It’s nice to get more confidence and sharpness in the legs, and my form is a big part of my body feeling good and the injury being a lot better.
“Wales feels like home now, the boys have been a big part of that and my partner and I feel really settled here in Cardiff.
“Injuries have played a role so far but I’m really looking forward to the future, starting with hopefully two more games with Cardiff Blues and another opportunity to play at the top level.”
The Blues face Stade Francais in a semi-final play-off for the last remaining place in the European Champions Cup next weekend. If successful they will then face the winner of Northampton Saints/Gloucester v Connacht in the final.
Anscombe will then link up with Wales ahead of the summer Test matches against Tonga and Samoa.
