The extension was confirmed just a day after his previous deal with the club of his life had expired.
Despite interest from MLS side Atlanta United, the 34-year-old has chosen to remain in the Spanish capital and will keep the captain's armband for the 2026-27 season, his 18th with the first team.
Koke made his debut on 19 September 2009, and has since made 740 official appearances for Atletico, scoring 50 goals and providing 122 assists.
He is also the club's all-time appearance leader and has won two LaLiga titles, a Copa del Rey, two Europa Leagues, two UEFA Super Cups and a Spanish Super Cup during his time at the Metropolitano.
Sources at the club say there was never any real doubt over his continuity, with the mood described internally as fully aligned on a renewal that has now been made official.
Koke remains the only player to have featured in all eight trophies won under Diego Simeone, forming what is regarded as the most successful partnership in the club's history.
"It's a source of pride to be able to stay at the club of my life for another season," said Koke.
"Personally, last season was very special for me because I was able to compete at a high level and help my team-mates where I like it most, out on the pitch. I'm proud to be able to help my team-mates, both on the pitch and off it. And I hope it's not just one more year, but many, and we'll work towards that."
Koke also set out his ambitions for the club collectively going forward.
"Collectively, which is what's most important, the target has to be winning a trophy. We've gone a few years without doing it, and neither the fans, the team nor the club can think about anything other than winning a title and getting back to Neptuno, where we all want to be."
The renewal ties the captain to Atletico for at least one more year, extending a partnership with the club that began when he broke into the first team as a teenager.
With the armband secured for an 18th consecutive season, Koke's next target is adding to a trophy cabinet that has stood still in recent years despite the consistency of his own performances.