Iwakuma (10-4), who won his third straight decision, struck out nine and walked one. Since moving into the starting rotation on July 2, 2012, Iwakuma has gone 18-8 with a 2.78 ERA in 38 starts.
Against the Twins, Iwakuma is 4-0 and hasn't allowed an earned run in 26 2-3 consecutive innings over his four starts Minnesota's third longest streak. He has held the Twins to a .168 batting average with eight walks and 24 strikeouts.
Felix Hernandez, who starts Friday, has the fourth longest streak at 24 straight scoreless innings.
Nick Franklin hit a three-run home run in the Mariners' big second inning. Dustin Ackley had three hits, including two doubles, and two RBIs.