Iwakuma (6-1) gave up seven hits and walked two to drop his ERA to 2.13, and Jesus Sucre added two hits and an RBI for the Mariners, who snapped Minnesota's four-game winning streak. Tom Wilhelmsen picked up his 12th save.
"With what he's done in the past, I think we're coming to expect this from him," Mariners shortstop Brendan Ryan said. "Whether that's fair or not, it's just a tribute to how good and how nasty he is."
Mike Pelfrey (3-6) gave up three runs on six hits in 5 1/3 innings for the Twins. Pedro Florimon had three hits and Chris Parmelee had two, but the rest of the lineup went 2-for-27 with six strikeouts.
Morales' eighth homer of the season was a two-run shot off Pelfrey to dead center field that started Seattle's three-run third inning. And that was all Iwakuma needed.
"He knows how to dig deep when he needs to and he understands the game, and great heartbeat, like we've talked about so much," Mariners manager Eric Wedge said. "He's able to slow the game down when he needs to slow it down and when he gets on a roll he gets in that nice tempo, which we've seen a lot of that this year."
After a 10-game losing streak earlier in the month, the Twins came into the opener against the struggling Mariners on a nice little roll. They had won five of their previous six games following that miserable skid and appeared to have their fortunes turning thanks to a soft spot in the schedule -- they took four straight from the free-falling Brewers this week -- and some luck in not getting Mariners ace Felix Hernandez this weekend.
But Iwakuma is no picnic either.
Like many of his Japanese brethren who have come before him, Iwakuma has an almost hypnotic, unconventional delivery that plays with a hitter's eye level. His right leg flares out on the follow-through that has the potential to distract as his splitter reaches the plate. He went 9-5 with a 3.16 ERA in 16 starts last season, but the American League hasn't shown any signs of figuring him out in his second year.
The crafty right-hander entered the game with a 2.35 ERA, the third best in the American League and just ahead of Hernandez (2.38). His only loss of the season came in a 2-1 defeat at Houston on April 23 when he struck out 11 in five innings.
He didn't miss as many bats on Friday night, but he was just as effective. He got Joe Mauer and Ryan Doumit twice and also induced three comebackers to the mound as the Twins flailed away.
"He can spot that fastball at the knees and I don't know how you want to describe it, but it's downhill and then it kind of flattens out," Ryan said. "It looks like it's going to be a ball down and it stays at the knees for a strike. Then he throws a splitter off that. What are you supposed to do? I mean at that point you're almost having to guess."
The Twins had a chance to get on the board in the third inning with runners at the corners and one out. But a drawn-in Brendan Ryan made a nifty stab at shortstop on a hot shot from Jamey Carroll and made a sharp throw off one foot to get Parmelee at home plate.
"He pretty much shut us down," Twins manager Ron Gardenhire said.
Iwakuma caught a break in the fifth when Florimon's double down the left field line bounced into the seats for a ground-rule double, which prevented Parmelee from scoring. Carroll grounded out to end the inning.
"I didn't have a very good bullpen today," Iwakuma said through a translator. "I thought my balance wasn't right, but then I was able to make my adjustment during the game."
The Mariners have won four of six following and eight-game losing streak. ... Twins RHP Anthony Swarzak had a throwing error in the seventh inning, snapping the team's 11-game errorless streak one game shy of the franchise record. ... Twins GM Terry Ryan said the team would not activate OF Wilkin Ramirez when he is eligible to come off the seven-day disabled list on Sunday. ... RHP Aaron Harang (2-5, 6.51) will go for the Mariners on Saturday against RHP Kevin Correia (5-4, 3.96.).
Copyright by STATS LLC and The Associated Press
MINNEAPOLIS, MN - MAY 31: Hisashi Iwakuma #18 of the Seattle Mariners delivers a pitch against the Minnesota Twins...