The club confirmed the agreement after Collinson celebrated his 17th birthday. He had previously signed a scholarship deal in July 2026, having progressed through the academy since joining during his Under-15 season.
Collinson has established himself as a promising presence in Chelsea's youth ranks, with the club describing him as a confident and commanding goalkeeper. His progress was recognised last season when he made his Under-18 debut in the Premier League Cup.
That first appearance came in a 3-3 draw at Cobham, giving him an opportunity to step up from the younger age groups and experience football at a higher level.
The teenager has also gained experience with England's youth teams. He has represented the Young Lions at both Under-15 and Under-16 level, adding international exposure to his development at club level.
Chelsea's academy has continued to provide a pathway for young players to progress towards professional football, with the scholarship stage typically offering a bridge between schoolboy football and the demands of a full-time professional environment.
For Collinson, the new contract represents recognition of the work he has put in since arriving at Cobham. It also gives him the opportunity to continue developing within a club that has a strong history of producing and promoting young goalkeepers.
The next challenge will be to build on his Under-18 experience and compete for further opportunities as he moves through the academy system.