The 25-year-old Queensland and Australian star was already signed until the end of next year but the Cowboys have swooped to keep the feisty forward away from any potential suitors.
Cotter, who won the Wally Lewis Medal as State of Origin player of the series in 2023, Â joined the Cowboys academy as a 15-year-old while living in Mackay.
The re-signing of such a pivotal player is a boost for the club ahead of Saturday night's away clash with Canterbury. Both sides are on 34 points with the Bulldogs in fifth on for and against.
The winner will finish fifth and host an elimination semi-final while the loser will be relying on Manly getting beaten to Cronulla on Sunday in order to stay sixth and also host a final.
The Cowboys beat an understrength Melbourne 38-30 last week but must be better against the Dogs.
"The obvious thing to work on is our attitude defensively," Cotter said.
"We get that right and we are going to be a dangerous team. They have a strong team and it is not an easy feat playing down there so we need to turn up with the right intent."
Winger Murray Taulagi said Cotter "epitomises what it means to be a Cowboy, not only on the field but off it as well".
"You want that guy to be in your team. You don't want to play against him. I am very fortunate to come up through the ranks with him," Taulagi said.
"We have represented in Origin and for Australia together. Whatever jersey he puts on he gives it one hundred per cent and for him to be our captain until 2028 ... we are very lucky."
Reuben Cotter charges into the Storm defence during the Cowboys' last-out win. (Scott Radford-Chisholm/AAP PHOTOS)
Cotter was never going to leave.
"It was a no-brainer for myself and my family," Cotter said.
"My wife is from the Burdekin and I am from Mackay so it made sense for me to stay here and I am very excited to extend with the club.
"I am extremely grateful for what has happened the last couple of years especially after what happened (with injuries) at the start of my career.
"I am excited for what we are building. I love playing alongside this group and what we are working towards ... obviously a premiership."
Cotter wasn't blessed with natural gifts as a footballer but his commitment and selflessness has made him a player all his colleagues want to run out alongside.
"I never had much skill. Growing up I was always a worker and that is something I always wanted to build my game around coming through the ranks," he said.
9°C