The Travelers confirmed that Mosiello, 46, will step down following Friday night's game. In a statement, the club said he will serve as the recruiting coordinator and hitting coach at the University of Tennessee. He coached at the school in 1994.
Todd Takayoshi will take over as interim manager on Saturday before Bobby Mitchell assumes managerial duties on July 31.
"From day one here in Arkansas, I know I set high expectations and we put ourselves out there by saying we were going to field a winning team," Mosiello said. "I knew that with the coaching staff of Francisco Matos, Brandon Emanuel, Mike Metcalfe and Seth Walsh, along with the talented group we've been assigned this year, that we could do something special.
"If I'm going to leave professional baseball, then this is the group that I want to go out with."
On Tuesday, Mosiello managed the Travelers past Springfield to secure the title with a 36-31 first-half record. It was the team's 14th division crown.
"I'm just so proud of these guys," Mosiello said. "We've got the youngest group of position players and the second-youngest pitching staff, and they've been busting their butts all season."
He boasted of the aggressiveness and ability to overcome injuries by a team led by 2009 first-round pick Mike Trout, MLB.com's No. 1 prospect, whom Mosiello has managed in each of the last two seasons.
"It definitely hurts a little bit. He was my coach for three years now. He's doing what's good for him, doing what's good for his family and he deserves it," Trout said of his skipper's departure. "He's worked hard the last three years in pro ball, and he's getting an opportunity. You can't turn it down."
Garrett Richards, who won his seventh consecutive decision Friday, echoed Trout's sentiments.
"He's a tremendous teacher. He just knows so much about the game. He's really turned a lot of us who have had him for two years into quality ballplayers. .... No words can describe how much of a leader and good coach and student of the game he is."
"It isn't always pretty," Mosiello said Tuesday. "But we want to make sure we err on the aggressive side."
Mosiello has plenty of college experience, coaching at Cal State-Fullerton (1991-92), Tennessee (1993-94), Ole Miss (1995), Oklahoma (1996-2000), Arizona State (2001), Southern California (2007) and Auburn (2008). He also spent time in the Alaska Summer League and the Cape Cod League.
In his first stint with Tennessee, as an assistant, the Vols won consecutive Southeastern Conference championships behind R.A. Dickey and Todd Helton.
Mosiello spent two-plus seasons managing in the Angels organization, taking all three of his teams -- including Class A Cedar Rapids -- to first-half division titles. His record in the Angels organization stands at 196-147.
Mosiello spent four seasons in the Yankees' organization at Class A Charleston and owns a 393-304 mark as a Minor League manager.
"It's a great opportunity that the University of Tennessee and head coach Dave Serrano have presented me with," said Mosiello, who is childhood friends with Serrano and previously coached with him at Cerritos College.
"All the Travelers' fans have been great and Pete Laven's staff has been excellent. I want to thank [Angels general manager] Tony Reagins, Abe Flores and the Los Angeles Angels for the previous 2 1/2 years. I've enjoyed my time with the Angels, but the opportunity at Tennessee is too good to pass up."
"I think he stuck to the philosophy of the organization. This team is a good team, a good group of players. We're happy with the way he's leaving the club, from a performance standpoint and what these guys have gone and the way they've gelled," said Reagins.
Takayoshi, the Angels field coordinator and roving hitting instructor, is in his 10th season in the organization. He spent the 2004-05 seasons as the Travelers batting coach.
Mitchell is in his ninth year with the Angels. He spent five seasons as a manager with Rancho Cucamonga (2006-07) and Salt Lake (2007-10), going 361-350 overall. Mitchell, who played four seasons in the Majors, is the Angels roving outfield, baserunning and bunting coordinator.