Ackley drew a one-out walk to spark a four-run 11th inning Friday as the Rainiers completed a three-game sweep of the defending champion Memphis Redbirds with a 10-6 victory.
The title is the first for Tacoma since 2001, when the Rainiers and New Orleans Zephyrs were declared co-champions in the wake of the Sept. 11 attacks.
Ackley, the second overall pick in the 2009 Draft, reached base three times and scored twice. After the 22-year-old second baseman drew a free pass from reliever Eduardo Sanchez, Greg Halman and Matt Mangini singled to snap a 6-6 tie.
David Winfree was hit by a pitch to load the bases and Mike Carp extended the lead with an RBI single. Justin Smoak, another former first-round pick, capped the inning with a two-run single.
The Rainiers overcame a couple of obstacles on their way to the Triple-A National Championship Game. When skipper Daren Brown was promoted to become the Mariners' interim manager, hitting coach Jose Castro took over. Tacoma went 13-15 to close the season but turned things around in the playoffs.
"Nothing changed. The way we played the game was the same as when Brownie was here," Castro said. "We lived and died by the longball, and that's how we won. Great bullpen and we got it done."
Due to renovations at Cheney Stadium, the Rainiers played their home games in the first round of the playoffs at Seattle's Safeco Field. The entire Championship Series was played at Memphis' AutoZone Park.
Ackley joined Tacoma in mid-July after getting off to a slow start at Double-A West Tenn. The University of North Carolina product batted .275 with 21 extra-base hits in the PCL, wrapping up his first season as a second baseman.
"I think it went great as far as my progress went," he said of the transition. "I still feel like I have a lot of improvement in some areas, but I feel like I've come a long way and I couldn't be happier with where I am at now."
The Rainiers' leadoff hitter was a spark plug in the playoffs, leading the league with 10 runs scored and tying for second with teammate Mike Wilson with seven RBIs.
"It's a great feeling," Ackley said. "I've been on some good teams my first year. I got called up to a team that was in first place and it's been great. It doesn't surprise me that we went this far in the playoffs."
The Rainiers' reliance on the longball was evident in the clincher as Ackley, Wilson and Eliezer Alfonzo slugged solo homers and David Winfree smacked a three-run blast. Tacoma totaled 11 homers in the three-game sweep after leading the PCL with 185 during the season.
"Winfree's been a force all year and so has Mangini. We have a lot of guys who can do a lot of things," Ackley said."I have a lot of good guys behind me and they can drive the ball."
The Rainiers are the second Mariners affiliate to win a championship following short-season Everett, which captured the Northwest League crown earlier this month.
"It's the whole organization, it's a great organization," Castro said. "Our farm director, Pedro Grifol, along with everyone else do an outstanding job, not only on the baseball side but outside the lines. It's an honor to be part of this organization and to win the PCL."
It's the first team Castro has managed to a championship. The 52-year-old has spent most of his career as a hitting instructor.
"It's an unbelievable feeling," he said. "Just like every other team you run for six months and you get to this point and it's indescribable unless you've been through it. Great feeling."
Andy Baldwin (1-0) struck out two over two perfect innings for the win and Josh Lueke allowed a hit and a walk in a scoreless 11th. Starter Yusmeiro Petit was charged with four runs -- two earned -- on six hits while striking out seven over five frames.
Mark Hamilton homered and drove in four runs for the Redbirds, who swept Sacramento in three games to win last year's championship.