The 20-year-old captained Wales to second place at last year's Junior World Championships in France and has since played eight times for the Blues this term, a figure that includes Heineken Cup outings at Toulon and at home to Exeter.
"At Cardiff Blues we have some of the brightest young back row players in Welsh rugby, so the news that Ellis has agreed a new contract is absolutely fantastic," said Blues director of rugby, Phil Davies.
"Ellis is the former U20 captain for Wales and a very mature and intelligent young player, especially at the breakdown where he makes good decisions.
"He is a big talent and someone who will only get better. Ellis wants to develop as a No7 and also has the ability to play six. We are lucky to have the likes of him, Josh Navidi and Rory Watts-Jones in that position.
"We're pleased that we've retained his services because he would have undoubtedly attracted the attention of other clubs. But he wants to remain a Blues player and help this region get even stronger."
A product of the Blues Academy and the Wales age-grade system, Jenkins insists he was always set on signing for the Blues, especially now that he is getting regular first-team action with the region.
Jenkins made his debut back in October 2011 but didn't feature at all last season. He is fast becoming an integral part of the Blues set up, though, and is now desperate to establish himself as a regular contender, preferably in Sam Warburton's No7 shirt.
"I've been at the Blues since I was 14 and grown up with many of my current team-mates. I've enjoyed my development here and I always wanted to remain a Blue," said Jenkins.
"I enjoy the environment here, believe in the coaching staff we have in place and it's great to sign and now concentrate on the rest of this season. We still have a lot to play for and I want to feature as much as I can and get even more experience at this level.
"To captain the Blues last week was a huge honour and now I want to establish myself as a regional player. I've been involved the last few months and I'm hoping next season I can really kick on."