"It's a huge moment for him, but he was good tonight," said Stars coach Ken Hitchcock. "He had to earn it tonight. He had to work."
Lehtonen was particularly sharp in the first period when he made 15 saves, including some high-end ones as the Stars were holding a 1-0 lead in the game.
"It's pretty special to see him reach 300 wins, that's pretty spectacular for a goaltender," said Stars captain Jamie Benn. "He was the player of the game, and we let him know that after the game."
Tyler Pitlick scored two goals for the Stars, and Alexander Radulov, Remi Elie, and Benn also scored as the Stars (18-3-1) improved to 2-0-0 on their current road trip and won for the fifth time in their last six games away from home.
"It was the same thing we did against the Rangers. We pressured the puck hard on the forecheck, played a strong territorial start," Hitchcock said. "The first two periods were excellent. We got soft on the puck in the third, and the Islanders started to come at us, but the first two periods - and even the first shift in the third period - we played really well."