Former Wales Under-20 skipper and openside flanker Jenkins has made 83 appearances for the Blues since making his debut in 2011.
His contract in the Welsh capital expired this summer, but he has now put pen to paper on fresh terms.
Jenkins is pleased to commit his future to the Blues and is now focused on returning to action in the coming weeks following a recent hamstring injury.
He said: “I’m really happy to sign a new contract here. I’ve come through the Cardiff Blues system, it’s a region I’m very passionate about, and I’m really optimistic about the future.
“It’s been great seeing so many of the other boys signing new deals and you only need to look at the likes of Dillon Lewis, Seb Davies and Owen Lane to see the talent coming through.
“I feel this is the best environment for me to continue improving and the competition for places in the back-row can only be beneficial to us all.
“I’m now looking forward to getting back on the pitch and contributing as much as I can in the second half of the season.”
Since making his debut six years ago, Jenkins has become an increasingly influential figure at the Arms Park.
He has led the Blues on several occasions and was rewarded for his fine regional form with a place on Wales’ 2016 summer tour to New Zealand.
He also featured on Wales’ summer trip to Tonga and Samoa earlier this year.
Cardiff Blues chief executive Richard Holland said: “It was always a main priority for us to retain the services of Ellis.
“He is a key figure and leader for us both on and off the pitch and will be instrumental in driving our rugby department going forward.
“He exudes all the qualities you would expect in a leader and is another example of a young, home-grown player to have come through our pathway.
“It came as no surprise that there was rival interest in his signature, but we are delighted he is staying at the Arms Park and are looking forward to seeing him back in action, and doing what he does best in the coming weeks.”
