Moyer, who has won 145 games since joining the Mariners in 1996, will be reunited in Philadelphia with former Mariners general manager Pat Gillick.
Moyer's career record is 211-164 with a 4.17 ERA in 563 games (510 starts). He was 145-87 with a 3.97 ERA in 324 games (323 starts) with Seattle.
"It's not a thrill," Seattle general manager Bill Bavasi said when asked how he felt about dealing Moyer. "He's meant a lot to this franchise and the community. He has done a great job for the organization. We thank him and we wish him well."
Moyer wasn't in Anaheim on Saturday, having flown back to Seattle, and wasn't available for comment.
"We felt this was a good trade for us," Seattle manager Mike Hargrove said. "And Jamie ... you wouldn't trade someone of his stature easily. He brought a professionalism that a lot of young kids can see and emulate. I don't know if I've ever seen a player prepare daily like he did."
In return for Moyer, Seattle acquired two right-handed pitchers who were pitching at the Class A level -- Andrew Barb and Andrew Baldwin -- along with cash considerations.
The 23-year-old Baldwin -- who projects as a starting pitcher -- was 8-8 with a 4.04 ERA to go with 100 strikeouts and just 22 walks for Class A Clearwater. He played at Texas A&M and Oregon State.
The 21-year-old Barb was 6-2 with a 2.23 ERA with 71 strikeouts in 60 1/3 innings as a reliever with Class A Lakewood. He is from Redmond, just outside Seattle.
Neither Baldwin nor Barb weren't ranked among Philadelphia's top 10 Minor League prospects before the season by Baseball America.
Baldwin compares to current Seattle pitcher Mark Lowe. He's got good size (6-foot-5, 215 pounds) and hit 94 mph in college. He's considered a pitcher with raw talent who could project to something.
As for Barb, he's mostly a fastball pitcher who throws a lot of strikes but could use a breaking ball to complement his fastball.
"We ended up getting two Minor League pitching prospects, which is something we are always looking for," Bavasi said. "I think our scouts did a good job. I feel we have good info on these guys."
The deal happened fast, according to Bavasi. Associate general manager Lee Pelekoudas had been in talks with Phillies assistant general manager Ruben Amaro about swinging a trade for Moyer, who will be a free agent after the season.
"We've got the potential for three openings in the rotation [next season], but we have to start looking now," Bavasi said.
Gil Meche, like Moyer, will be a free agent after the season. Another starter, Joel Pineiro, will be eligible for salary arbitration.
The deal wasn't consummated until shortly before Seattle began play on Saturday against the Los Angeles Angels at Angel Stadium.
"It's been pretty quick," Bavasi said.
In order to make the trade go through, Moyer, who has 10-and-5 rights (10 years in the Major Leagues, five consecutive years with the same team), had to approve it.
Moyer is from Sellersville, Pa., and attended St. Joseph's University, where he had his number retired and was inducted into the school's Hall of Fame in 1987, which could have been a factor in accepting a trade to the Phillies, who are contending for the National League Wild Card berth.
"He wanted to pitch for a club that had an opportunity to go to the playoffs," Gillick said of Moyer, who serves as his own agent. "He not only brings experience, but this guy can win. He's kind of a guy who's flown under the radar for a long time."
This surely isn't the first time the Mariners have been approached about moving Moyer. Last season, Moyer reportedly blocked a trade before the July 31 non-waiver deadline to Houston.
Moyer came to Seattle from Boston in 1996 for outfielder Darren Bragg. Moyer went 6-2 in the second half of that season and then won 17 games the following season.
Moyer's best season with the Mariners came in 2003, when he went 21-7 with a 3.27 ERA in 33 starts.
"It's a weird feeling," Meche said. "Jamie was great. I hope he does well. I thought this might be something he'd do. Our team got real young in a hurry."
Corey Brock is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.