Bonds broke Mark McGwire's 1998 home run record of 70 by hitting 73, and had the highest slugging percentage (.863) and most walks (177) in a single season. Both records had been held by Babe Ruth.
"It's a tremendous award, and it's very much appreciated because all the players voted for it. I'm honored," Bonds said.
Previously named as the Player of the Decade for the 1990s by The Sporting News, Bonds also hit his 500th career homer and moved into seventh place on the all-time list with 567 this season.
It is the second time that Bonds has won the honor, having first captured the award in 1990 while with the Pittsburgh Pirates. He joins Ted Williams, Stan Musial, Joe Morgan and Cal Ripken Jr. as the only players to capture the award twice.
Piniella guided the Mariners to a major league record-tying 116 wins, matching the 1906 Cubs. After the departure of Alex Rodriguez, the third superstar the Mariners have lost since 1998, Piniella coaxed contributions from every player on the roster.
"We've had a good year here, and our organization shares in this award," Piniella said.
With eight votes, Piniella finished ahead of Art Howe of the Oakland Athletics, who received 3 1/2 votes, and Tom Kelly of Minnesota, Jimy Williams, who was fired late in the season by Boston, and Charlie Manuel of Cleveland.
Bowa's abrasive style did not make him popular with the players, but he transformed a team which lost 97 games in 2000 to an 86-76 club this past season.
"A manager is only as good as his players, and I owe this to all their hard work," Bowa said.
The Rookies of the Year were Ichiro Suzuki of the Seattle Mariners and Albert Pujols of the St. Louis Cardinals. The Rookie Pitchers of the Year were C.C. Sabathia of Cleveland and Roy Oswalt of the Houston Astros.
The Comeback Players were Ruben Sierra of the Texas Rangers and Matt Morris of the Cardinals.
The Executive of the Year will be announced at the winter meetings in December.