Kane announced the contract on his Twitter account early Wednesday, saying "I'm back."
"Throughout the last 12 months there have been lots of road blocks, tons of adversity and many tough days," Kane wrote. "I'm grateful for the tremendous amount of support from family, friends, teammates and others who have helped me stay strong through those difficult times."
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The 30-year-old forward had 39 points (22 goals, 17 assists) in 43 regular-season games for the Oilers last season and 17 points (13 goals, four assists) in 15 Stanley Cup Playoff games.
Kane signed with Edmonton as a free agent Jan. 27, after his contract was terminated by the San Jose Sharks on Jan. 9. He did not play for the Sharks last season after being suspended by the NHL for 21 games Oct. 18 for violating NHL COVID-19 protocol.
Kane was the subject of two investigations prior to his suspension. The NHL announced Oct. 18 allegations of domestic abuse by Kane's estranged wife, Anna, could not be substantiated after announcing Sept. 22 it found no evidence to support allegations that he gambled on NHL games or tried to negatively impact Sharks games.
Video: Evander Kane\ staying in Edmonton
"We've had four or five months with him and he fit in real well," Oilers general manager Ken Holland said of Kane. "At the end of the year when I went through the exit interviews with the players, to a man, everybody in that locker room wanted him back and they made that very clear to me. They felt we were a much better team with Evander on our team. … I'm comfortable with the four (years). He's 31 years of age and if you look at him, he's probably around a 25-30 goal scorer before he got here and he found tremendous chemistry with Connor (McDavid) and Leon (Draisaitl), especially with Connor. He was on pace for 40-45 goals with us. He brings and edge to his game, some personality, some physicality, so it's not only the ability to score goals, it's also the other dimensions he brings to our team are also very valuable.
"I wanted to find a solution that worked for Evander and I was comfortable with a four-year contract."
Kane tied with Nathan MacKinnon of the Stanley Cup champion Colorado Avalanche for most goals in the postseason. The Oilers reached the Western Conference Final, where they were swept from the best-of-7 series by the Avalanche.
"A big part of my decision to stay in Edmonton was because of the opporunity given to me only seven months ago but also the chance to be apart of a championship team," Kane wrote. "I want to win, and I believe after signing this deal we will be able to add the right pieces along with myself to accopmplish that goal, a championship.
"See you in the fall."
Selected by the Atlanta Thrashers in the first round (No. 4) of the 2009 NHL Draft, Kane has 545 points (286 goals, 259 assists) in 812 regular-season games for the Oilers, Sharks, Buffalo Sabres, Winnipeg Jets and Thrashers and 30 points (19 goals, 11 assists) in 43 playoff games.
Tweet from @evanderkane\_9: I���m back. pic.twitter.com/aBAw0dQlNL