Patchell, who was tipped as an outside chance to make Wales' RBS 6 Nations squad this season, has penned fresh terms alongside Sam Hobbs, Rhys Williams, Tom Davies and Richard Smith.
"I think that we need to retain all our outstanding young players and hopefully those we have signed for next season, such as Matthew Rees, will help add value and experience to the squad," Blues rugby director Phil Davies said.
"The current squad will be a lot better and we will be a lot stronger next season.
"We just have to go along with the principles we have this season - trying to get 25 players under the age of 25 at the club for the next three or four years.
"We are building it around that number and age pool so we can start challenging the likes of Leinster and Ulster, or any other team for that matter."
- Sports & Recreation
- Tom Davies