The 21-year-old, the 271st overall draft pick in 2003, had made 30 saves to give the Montreal Canadiens a 1-0 victory over the Boston Bruins that they desperately needed to stay in the Eastern Conference playoff race.
Not bad for a goaltender the Canadiens considered returning to AHL Hamilton only last week.
"It's going to be a good souvenir for me," he said. "I kept the pucks for all my (six) shutouts in Hamilton, except one that the referee took. But this is the biggest one, for sure."
The win gave Montreal (37-31-6) 80 points, tied with eighth-place Toronto and Carolina, but those two clubs each have a game in hand.
The New York Islanders dropped to one point back in 11th place, while Boston fell to seven points out of playoff position with 10 games to go.
Another rookie provided the offence, as Guillaume Latendresse scored the game's only goal with a deft move at 19:00 of the second period.
The Canadiens had picked up the tempo after a flat opening 30 minutes and began to create chances on Boston goaltender Tim Thomas.
Mike Komisarek sent a two-line pass that was tipped to Latendresse at the Boston line. He put a deke on Aaron Ward and went in alone to score.
"That mistake was a killer," said Ward. "I got surprised by the pass, but it's unacceptable to have a guy walk in like that.
"But it was a good play on his part."
Halak, who was tearing up the AHL, was called up to Montreal on Feb. 15 after No. 1 goalie Cristobal Huet tore a hamstring and needed surgery.
The Slovak was on a high after winning his first three NHL starts, but then lost four in a row - the last a 6-2 shellacking in Atlanta on March 8 from which he had to be pulled.
That's when Montreal management considered shipping him back to Hamilton, but when David Aebischer played poorly, coach Guy Carbonneau opted to give Halak one more chance.
He shone in a 3-2 shootout win over the rival Toronto Maple Leafs in an emotionally charged atmosphere at the Bell Centre on Saturday, then shut out the Bruins.
He is certain to be back in goal when the teams meet again Thursday night in Boston.
"When he came up, everything was new to him," said Carbonneau. "He just wanted to have fun and play well. He won three in a row, and sometimes you start feeling the pressure then and start thinking differently.
"He had a chance to sit back and see what's going on and I think he's better prepared now. You can see it in the net. He looks better. I think the experience he gained a couple of weeks ago will be beneficial to him."
He also had some luck, especially late in the third period with the Bruins pressing for the equalizer. A shot from the point from fellow Slovak Zdeno Chara hit Halak on the pads while he was looking away.
"I didn't see it, there were too many guys in front of me," Halak said.
The Bruins were shut out for a second game in a row after a 7-0 thumping by the New York Rangers on Saturday night. Montreal posted its fourth win in the last five games.
Instead of playoff-race intensity, the first period produced only sporadic chances as both clubs struggled on what looked like slow ice and the crowd of 21,273 was unusually quiet.
It took until midway through the second frame for Montreal to begin getting the puck in deep, shooting from every angle, and looking for traffic in front of Thomas, and that's when their best chances came.
Steve Begin hit a post from the slot, and Alex Kovalev had a shot into an open side tipped high on a brilliant Thomas save just before Latendresse finally broke the ice.
Latendresse has five goals in his last six games.
Notes - With the return of C Radek Bonk from a flu, D Mathieu Dandenault returned to the defence and D Josh Gorges was scratched. F Garth Murray, F. Sergei Samsonov and F Alexander Perezhogin (concussion) also didn't play. . .Shean Donovan (sprained knee), Glen Murray (knee) and P.J. Axelsson (wrist) didn't play for Boston.