The 50-year-old American, a two-time MLS Cup champion coach, went 23-13-39, guiding the Revs in all competitions over nearly two seasons since taking over from Bruce Arena before the 2024 campaign.
The Revolution's record after last Saturday's 1-1 draw with Toronto is 8-8-14 for 32 points, 10 points out of the last Eastern Conference playoff berth, with four matches remaining.
Assistant coach Pablo Moreira will serve as interim head coach for the remainder of the campaign.
"I'm very grateful to Caleb Porter for the energy, effort, and dedication he has brought to the Revolution over the last two years," Revolution sporting director Curt Onalfo said.
"I have the utmost respect for Caleb and all the tireless work he has invested in the club, and we wish him the best moving forward."
Porter has an MLS career coaching record of 160-144-11, having guided the Portland Timbers to the 2015 MLS Cup crown and the Columbus Crew to the 2020 league title.
But the Revolution missed last year's MLS playoffs and are on pace to do so again this season.