C.J. Cron also went deep for the Rockies, and Connor Joe had three hits.
In the opener, Starling Marte homered in his return to the lineup as the Mets rolled to a 5-1 victory.
Friday night's scheduled game was postponed when wintry weather blew into Colorado after temperatures were in the high 80s on Thursday. Snow continued to fall Saturday morning but the sky cleared before the first pitch of the day. Temperatures were in the 40s for both games.
Serven, who went 0 for 2 in his major league debut Wednesday, homered in the second inning off Trevor Williams (0-3) to put Colorado ahead 4-2. Batting ninth, the rookie catcher added a two-run shot in a seven-run sixth.
''I didn't think the second one was gone when I hit it,'' Serven said. ''I thought I hit it too low. I knew I hit it well but I didn't think it was going to get out.''
Serven also threw out J.D. Davis trying to steal second to end the sixth inning.
''Those are special moments. It's awesome. I love it,'' Rockies manager Bud Black said. ''Two good swings. He took advantage of a couple of breaking balls that were hung.''
Ashton Goudeau (1-0) pitched 2 2/3 innings of relief to earn the win.
Carlos Carrasco (4-1) allowed a run on seven hits in 5 1/3 innings and Luis Guillorme had three hits in the opener for New York.
Marte was away from the team following the death of his grandmother and was reinstated from the bereavement list before the first game. His first swing of the day went deep into the left-field bleachers to give the Mets a 2-0 lead two batters into the game.
''We all just kind of looked at each other and went, `Really?' You can't make that stuff up,'' Mets manager Buck Showalter said. ''It was emotional. I'm glad I had glasses on.''
When Marte crossed home plate he looked up and pointed to the sky.
''It's a hard situation because it's one of those things that's going to be in my mind for a very long time,'' Marte said before the game about his grandmother's death. ''Being around the team is a distraction, but...you have to go through it.''
Patrick Mazeika had a two-run double in the second inning to stretch New York's lead and Francisco Lindor's RBI single in the sixth made it 5-0.
Cron had three hits and German Marquez (1-4) allowed five runs - four earned - in six innings for the Rockies.
Carrasco left after Brendan Rodgers singled in the sixth inning. Jose Iglesias hit a grounder in front of the plate and beat the throw to first, allowing Cron to score from third.
''This is my first time pitching here,'' Carrasco said. ''Normally when I throw my changeup it's completely different. Here it looked like more like a two-seamer.''
The Mets and pitcher Chris Bassitt agreed on a one-year, $8.8 million contract with a mutual option for 2023. The agreement avoided an arbitration hearing that would have taken place Monday.
Bassitt, acquired from Oakland on March 12, is 4-2 with a 2.77 ERA in eight starts. He said he is glad to get the deal done.
''I didn't want to go to trial,'' Bassitt said after the first game. ''I like everyone here. I think we have a really great relationship here and just why even remotely try to mess with that? We have such a special group that I don't want to really be a distraction and hurt that in any way.''
Despite injuries to the rotation, Bassitt thinks the team has a chance to win.
''We have a real chance to win a World Series and that's all I've been thinking about, just what it kind of takes to put our team in the best spot to do that,'' he said.
New York third baseman Eduardo Escobar accrued 10 years of major league service and was celebrated by the team, which made a video to mark his milestone. The Mets gave him a bottle of champagne, but he won't open it yet.
''I'll drink it once we become champions,'' he said before Saturday's first game.
Mets: Showalter said RHP Tylor Megill (right biceps tendinitis) is scheduled to throw back in New York and will eventually make a rehab start. ... RHP Max Scherzer was placed on the 15-day injured list with a left oblique strain. The move is retroactive to Thursday.
Rockies: Iglesias didn't play in the second game due to a left elbow injury sustained in the opener. Iglesias was hit by a pitch on the joint and it swelled up. Black said it was likely not a long-term issue. ... OF Kris Bryant (back strain) was activated from the injured list. Bryant had not played since April 25 in Philadelphia. He singled in four at-bats in the first game.
Mets RHP Taijuan Walker (1-0, 3.52 ERA) faces LHP Austin Gomber (2-3, 4.38) on Sunday.
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