The 22-year-old defenseman was a restricted free agent. He had NHL career highs in goals (13), assists (38) and points (51) in 80 games last season.
"Obviously really excited," Dobson said Monday. "Looking back to the second half of the year, I was happy with the steps I took, and I think just coming into the offseason, just try to really use the extra time. We've have to take another step this year, and just excited about the next three years to be able to continue and grow and build off my year last year."
Selected by New York in the first round (No. 12) of the 2018 NHL Draft, Dobson has 72 points (17 goals, 55 assists) in 160 regular-season games, and seven assists in 20 Stanley Cup Playoff games.
"What I like about him is what most of us see, his hockey instincts and his offensive capabilities as far as reading plays," Islanders general manager Lou Lamoriello said.
Lamoriello said a key to Dobson's development was his willingness to be patient, which included sitting out some nights the past two seasons. He played 34 games as a rookie in 2019-20, and 46 games in 2020-21.
"He had the patience and he had the self-discipline to just practice every single day, get an opportunity every so often and just grew as a patient player of growing strength," Lamoriello said. "Really worked at his game and had the opportunity to do that and put extra sessions in after regular practices because he knew he wasn't going to be playing.
"And then when he had the opportunity to get full time, as he did last year, he grew throughout the season, so I don't think there's any height to where he can go."
Defenseman Alexander Romanov (three years) and forward Kieffer Bellows (one year) also signed contracts on Monday.
Romanov, a restricted free agent, had been acquired in a trade with the Montreal Canadiens on July 7 for the No. 13 pick of the 2022 NHL Draft. The 22-year-old had 13 points (three goals, 10 assists) in 79 games last season.
Selected by Montreal in the second round (No. 38) of the 2018 draft, Romanov has 19 points (four goals, 15 assists) in 133 regular-season games, and one goal in four playoff games.
"Looking at the strengths, Alex is a good skater, he can be a good puck mover, and I think some of those attributes are some of my strengths as well," Dobson said. "So, I think having those tools can work well, especially breaking pucks out well in transition and the offensive zone. ... I'm really excited he's part of our 'D' core. He's going to be a great addition."
Bellows, who was also an RFA, had 19 points (six goals, 13 assists) in 45 games last season.
Selected by New York in the first round (No. 19) in the 2016 NHL Draft, the 24-year-old forward has 25 points (11 goals, 14 assists) in 67 games.
"I see myself as being a regular in the lineup," Bellows said. "That's what I want to be. I want to be making a big impact from Day One, and that's what I plan to do. I plan to be good defensively but bring offensive flair, use my shot and score some goals for this team. I expect myself to have a great year."
NHL.com staff writer Jon Lane contributed to this report
