Stanton's three-run homer came a day after the slugger provided the only hit Miami had in Sunday's 7-0 loss to the Yankees in Panama.
"I didn't feel too comfortable down in Panama, but those were a couple of days you had to get through and jump back into it," Stanton said.
Garrett Jones and Jarrod Saltalamacchia hit back-to-back RBI singles in the first inning off John Lannan. The Marlins tagged the Mets lefty for five runs on eight hits in 3 1/3 innings. He walked four.
"I just had a bad day, just couldn't find the strike zone," Lannan said. "Everything felt pretty good. I was just missing the plate. Curveball, slider, everything was kind of falling off, and I really couldn't command the strike zone like I did the previous couple of outings."
The Marlins have enjoyed strong starting pitching all spring, and Henderson Alvarez continued the trend, giving up one run in four innings. The right-hander allowed three hits, walked two and struck out five. His afternoon concluded after 66 pitches, with 41 strikes.
"I attacked the zone," Alvarez said. "I attacked the hitters. I tried to throw all my pitches for strikes."
Anthony Recker plated the lone run off Alvarez with a single in the fourth inning.
In the eighth inning, the Mets scored five runs off Chaz Roe to make it a two-run game. Anthony Seratelli and Zach Lutz had RBI singles, and Juan Centeno lifted a sacrifice fly. Clark's two-run single came off Carter Capps, with both runs charged to Roe. Roe threw two wild pitches, and Capps had one in the inning.
Up next: Jacob Turner is looking to lock down the fourth-starter spot for Miami. On Tuesday, the right-hander, who is 1-1 with a 4.32 ERA this spring, will go against the Astros at Roger Dean Stadium at 1:05 p.m. ET. Houston will start Dallas Keuchel, who was effective against Miami early in Spring Training.
Joe Frisaro is a reporter for MLB.com. He writes a blog, called The Fish Pond. Follow him on Twitter @JoeFrisaro. This story was not subject to the approval of Major League Baseball or its clubs.