The 19-year-old back-row, one of Welsh rugby’s bright young prospects, has made a big impression at Parc y Scarlets this season and came off the bench for his Guinness PRO14 debut against Leinster last month.
The son of Tongan international Kati, Tuipulotu was educated at Sedbergh School in Cumbria before linking up with the Scarlets Academy from Newcastle Falcons two seasons ago.
Capped at Wales Under-16 and Under-18 level, he is currently part of the Wales Under-20 group training for the forthcoming Six Nations.
He is also in the first year of a philosophy degree at Swansea University and combining his studies with his professional rugby career.
“I am delighted to have signed a contract here with the Scarlets,” he said.
“I feel like I am settled and really at home here. There are a lot of senior players who have been a great help to me. They are like my big brothers. I am learning a huge amount from their experiences and that can only help me develop my game.
“It was great to get a taste of the PRO14 against one of the best sides in the competition in Leinster and hopefully it will be the first of many.
“For me, it is a case of working hard in training and to keep on learning. I am looking forward to seeing what the future holds for me at the Scarlets.”
Scarlets head coach Glenn Delaney said: “Carwyn is clearly a young man with a big future ahead of him and it is great news he has signed a four-year contract with the Scarlets.
“Athletically, Carwyn is phenomenal and we feel a real responsibility to provide him with the best opportunity and environment to progress. It’s about making sure we do the right thing by him so he can become the player we all hope he will be.
“He has already made a big impact around the group and one of the plans we had with Sione Kalamafoni coming to the club was to provide a bit of mentorship from a man who understands how to train and how to be an ultimate professional.
“Carwyn has already had a taste of senior rugby and I am sure Scarlets fans are looking forward to seeing a lot more of him over the coming seasons.”