Lee, who led the team with 94 RBIs last season but had none in 19 spring at-bats prior to Sunday, shot a double to right in the first inning to score Jordan Schafer and Travis Buck, and then clubbed a 1-0 pitch high over the left-field wall in the second to put the Astros ahead, 7-4.
Pelfrey's spring struggles continued. He pitched 2 2/3 innings and allowed eight hits, eight earned runs and four walks while striking out four batters. In three starts this spring, Pelfrey has allowed 16 earned runs in 9 2/3 innings.
Schafer walked twice and scored two runs before leaving the game in the third after he appeared to injure his wrist or hand making a running, diving catch.
Buck got the start in right field for the Astros and doubled and singled ahead of Lee, scoring a pair of runs. Jed Lowrie knocked a two-run double in the second inning, and Jimmy Paredes scored on a Pelfrey wild pitch in the third to make it 8-4.
Lowrie added a homer to lead off the sixth, and Buck followed with his third hit and second double of the afternoon.
Astros starter Livan Hernandez worked three-plus innings, allowing five hits, four runs and three walks in his fourth start of the spring.
The Mets' early offense came from Ronny Cedeno, who clubbed a solo homer in the first, and Vinny Rottino and Mike Baxter, who knocked RBI singles in the second. Pelfrey contributed an RBI groundout in the frame.
Up next: The Mets are off Monday, their only break in the Grapefruit League schedule. Play resumes at Digital Domain Park on Tuesday with a 6:10 p.m. ET game against the Cardinals. Right-hander Dillon Gee is scheduled to start, with relievers Jon Rauch and Frank Francisco also booked to make appearances.