Twelvetrees became Gloucester's first British & Irish Lion since Phil Vickery when he was called away from the England tour of Argentina to join the squad Down Under as cover for the back division.
The former Leicester Lions and Bedford Blues player made his debut in the 14-12 defeat to the Brumbies in Canberra on June 18, playing the full 80 minutes before making a second tour appearance as a first half replacement for Brad Barritt in the 35-0 victory over the Melbourne Rebels.
And the Chichester-born star has continued his fine form since returning to domestic duties, kicking the winning penalty as Gloucester overcame Northampton Saints 26-24 to win their first Premiership game of the season last weekend.
"I'm really settled here," said Twelvetrees. "The club has been great to me, and this has seen me develop my game and ultimately earn international recognition.
"I've made great friends here and, to continue playing with the lads and developing partnerships, is something that I cannot wait to continue.
"We as players, speak a lot about how great the Gloucester fans are and, to play in front of the fine support we have as a club, is all you can ask for as a player.
"The team is still developing and the talent and potential here is great. So, I can't wait to see where we go and what we can achieve, and I couldn't imagine not being part of it."