Iwakuma (13-6) matched his career high going eight innings, giving up just four hits and one unintentional walk. He struck out six, including Cabrera twice.
"You don't see many pitchers have Miggy swinging like he was out there," Mariners manager Eric Wedge said.
Iwakuma's 25-inning scoreless streak on the road matches a franchise record. It trails only the 25 2/3 innings scoreless stretch Joe Kelly had on the road for St. Louis earlier this year, according to STATS LLC.
"I don't know what I might be doing to make it happen," the Japanese right-hander said through an interpreter. "I'm just trying to focus, pitch my game and stay with my plan."
Iwakuma, who became an All-Star this year in his second season, joined Randy Johnson (1994) and Brian Holman (1989) as Mariners who have thrown 25 straight scoreless innings on the road.
In the fourth inning, Iwakuma got out of a bases-loaded jam for the second time in the game at Detroit.
"We had a shot," Tigers manager Jim Leyland said. "But that's what good pitchers do, they don't let you capitalize.
"That's why he's one of the best."
Verlander (13-12) allowed three runs, four hits, walked three and struck out six over seven innings.
"The stuff has been getting better almost every time out," Verlander said. "How I'm going to be in the postseason, we'll see. You never want to say anything clinched until it is."
The AL Central-leading Tigers had won three straight and six of seven to close in on their third straight title, but they have not eliminated the Cleveland Indians from contention in the division.
Seattle had lost eight of nine.
Verlander gave up walks to leadoff hitters in the first two innings, and the second time it led to him giving up two runs.
"The walks hurt me," Verlander said. "It seemed like every inning, especially the first four, I was very erratic with the first batter of the inning."
Verlander seemed to finally find a groove in the fourth inning when he retired the side in order, but Smoak's solo shot -- his 17th homer -- gave Seattle a 3-0 lead in the sixth.
Verlander struck out two in the seventh, ending his 124-pitch outing.
The 2011 MVP and Cy Young Award winner earned a victory in his previous start, ending a six-game winless streak. He has won consecutive games only once -- July 31 and Aug. 6 -- since winning four straight starts in late May and early June.
Iwakuma, meanwhile, hadn't won any of his previous four starts despite a 2.10 ERA over that stretch.
He didn't need more run support against Detroit, but the Mariners provided it four runs in the eighth and another in the ninth on Gutierrez's homer.
The Tigers gave OF Torii Hunter a scheduled day off and rested 2B Omar Infante. ... Tigers RHP Bruce Rondon, who hasn't pitched in a game since Sept. 2 because of an elbow injury, threw from 120 feet on Wednesday and the team hopes he can throw a bullpen session by the end of the week. ... Smoak has six homers over 11 games in Detroit. ... The Tigers announced Larry Parrish will be retained to manage the Triple-A Toledo next year. ... Detroit's Doug Fister (12-9) will start against Seattle's James Paxton (2-0) in the series finale Thursday, then the Tigers will open their home series against the Chicago White Sox on Friday night when Max Scherzer will make his fifth straight start seeking his 20th win.