Franklin, Brad Miller and Kendrys Morales each drove in a run during a pivotal eighth frame that saw two runs come across on wild pitches as Seattle erased a 4-2 deficit.
The Mariners were outhit, 11-7, but held the A's to one hit in nine chances with a runner in scoring position as they improved to 4-4 on their nine-game road trip.
Josh Donaldson hit a two-run homer and Nate Freiman added a solo shot in the loss, just the second for Oakland in its last six games.
Sonny Gray, who was coming off his first big-league victory, twirled seven solid innings for the A's, the only costly mistake coming in the third inning when he served up a two-run homer to Franklin.
Sean Doolittle (4-5) relieved Gray in the eighth and did not record an out while blowing Oakland's lead. Michael Saunders led off the inning with a single and moved to third when Yoenis Cespedes dropped a line drive in left field off the bat of Henry Blanco, who was somehow credited with a double.
Miller and Franklin each followed with run-scoring singles to end Doolittle's unproductive night, and Ryan Cook walked Kyle Seager to load the bases before uncorking a wild pitch that allowed the go-ahead run to score.
Franklin slid in safely at home on Morales' chopper to second base, and Seager scored on another wild pitch from Cook for a 7-4 Mariners lead.
Brandon Maurer (4-7) left two A's stranded in the seventh, Yoervis Medina worked around a pair of walks in the eighth and Danny Farquhar set down the side in order in the ninth to record his eighth save of the season.
The A's jumped out to a 4-0 lead just five batters into their first at-bat against Mariners lefty Joe Saunders.
Jed Lowrie led off with a triple and scored on Derek Norris' base hit to right field. Donaldson followed with a home run over the 362-foot sign on the left- field wall, and two batters later Freiman sent one to the same spot, only his found the seats.
Saunders lasted six frames despite the shaky start and was charged with 10 hits, three walks and the four runs.
The A's fell to 45-6 when outhomering the opposition ... Gray was charged with two runs on two hits and two walks while recording seven strikeouts ... Alberto Callaspo had three hits for Oakland ... Seattle leads the season series, 9-6.
08/21 01:27:37 ET