The contract begins next season.
"Nic loves being a Vegas Golden Knight and we love having him," general manager Kelly McCrimmon said in comments tweeted by the team. "It was slower than we would've liked. These things sometimes drag on. We're really looking forward to getting Nic back in town."
The 23-year-old defenseman had 14 points (four goals, 10 assists) in 52 games last season for Vegas. He has 42 points (10 goals, 32 assists) in 142 NHL games, and two points (one goal, one assist) in 10 Stanley Cup Playoff games with the Golden Knights in the 2020-21 season.
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Selected in the second round (No. 34) in the 2017 NHL Draft, he was fifth among Golden Knights defensemen who played at least 30 games with an average time on ice of 18:40.
"You'll see a player still just scratching the surface," McCrimmon said. "Good offensive instincts. Those are the things that excite us."
The Golden Knights open the regular season against the Los Angeles Kings at Crypto.com Arena in Los Angeles on Tuesday (10 p.m. ET; ESPN, TVAS, SN1, SN NOW).
