"We are very happy to come to terms with Collen following the season he had last year," said sporting director Nick De Santis.
"He adapted well to the city, the culture and this organization. He was an important piece of our roster last year and played a vital role. We feel that he can be a key player for our team again this year and in the future."
Warner added: "I'm really excited to re-sign with the club and get this extension done before the start of the season.
"Now, I can focus all my energy on the upcoming season and on helping this team win games. I would like to thank the organization, the coaching staff, sporting director Nick De Santis and president Joey Saputo for giving me the opportunity to continue my career here in Montreal."