Colletti graduated from East Leyden High School in Franklin Park, Illinois, and attended Triton College before graduating from Northern Illinois University. He was inducted into the Triton College Sports Hall of Fame in 1993, the same year as the Major League players Kirby Puckett, Lance Johnson and Jeff Reboulet.
In 1982, Colletti began his Major League career with the Chicago Cubs. He was a member of the front office when the Cubs won the National League East in 1984 and 1989. Colletti was honored with Major League Baseball's Robert O. Fishel Award for Public Relations Excellence in 1990.
Colletti left the Cubs and joined the front office of the San Francisco Giants in 1994 as director of baseball operations. He was promoted to assistant general manager in October 1996. During his tenure, the Giants had an 813–644 overall record (.558), winning an average of 90.3 games per season. He was hired by the Los Angeles Dodgers in 2005. During his tenure with the Dodgers (2005-2014), Colletti had the highest winning percentage of any general manager in the National League.
Colletti became the 10th general manager in Los Angeles Dodgers history and the fifth in eight years when he was hired on November 16, 2005.
The Dodgers made the playoffs in five of his nine seasons from 2006–14. Only once in Colletti's nine seasons did the Dodgers have a losing record. Los Angeles went to the NL Division Series in Colletti's first season in 2006 and reached the National League Championship Series in 2008, 2009, and 2013. The back-to-back appearances in 2008–09 marked the first time the Dodgers had reached the NLCS in consecutive years since 1977–78. The Dodgers won 15 playoff games from 1989–2014. Fourteen of those playoff wins came under Colletti. The only other Dodger post-season win in that period came in the 2004 NL Division Series under then-GM Dan Evans.
During six of Colletti's nine seasons, the Dodgers set home attendance records. The Dodgers averaged 3,606,151 fans per season in Colletti's nine seasons with the Dodgers. The Dodgers led all of Major League Baseball in home and road attendance in 2013 and led, again, in home attendance in 2014 with 3,782,337 fans.
In 2010, under Colletti's leadership, the Dodgers were named Topps Organization of the Year, an honor presented annually to the Major League franchise that has shown most-outstanding performance, depth and talent among its Major and Minor League teams.
In the nine seasons from the start of Colletti's career as general manager through 2014, the Dodgers had a 783–674 (.537) record—the third-best record in the National League. Only the Cardinals (.542) and Phillies (.538) were better. Among NL West teams, the Dodgers' record during that stretch was 40 games better than second-best San Francisco Giants.
Colletti reached 750 wins as a general manager on July 29, 2014, when the Dodgers defeated the Atlanta Braves 3–2 in 10 innings at Dodger Stadium before a crowd of 47,386. Only Buzzie Bavasi reached the 750-win mark faster in Dodger history. His 783 wins from 2006–14 were most among all National League general managers.
From June to December 2012, Colletti, with the backing of a new, aggressive ownership team led by Dodgers' president Stan Kasten, owners Mark Walter, Earvin "Magic" Johnson, Peter Guber, and Guggenheim Baseball Management, spent more than $600 million to bring a parade of all-star players and prospects to Los Angeles. The wholesale makeover began in late June when the Dodgers spent $42 million to sign 21-year-old Cuban prospect Yasiel Puig to a six-year deal. On July 25, Colletti brought in former National League batting champion Hanley Ramírez as the key to a four-player trade with the Miami Marlins.
On August 25, 2012, with the Dodgers three games behind the Giants in the National League West and 1½ games out of the final wild card spot, Colletti completed a nine-player trade that the Los Angeles Times called a "block-buster" and a "stunning development". Key to the deal was the acquisition of four-time All-Star first baseman Adrian Gonzalez from the Boston Red Sox. But the Dodgers also obtained the four-time All-Star outfielder Carl Crawford, three-time All-Star pitcher Josh Beckett, and respected, switch-hitting utility infielder Nick Punto. The Red Sox received first-baseman James Loney and four prospects, including infielder Iván DeJesús, Jr. and pitcher Allen Webster. The Boston Globe's Dan Shaughnessy called it "the biggest Red Sox trade since Babe Ruth was dealt to the Yankees for cash in 1920",.
After ending the season 86–76, but failing to make the playoffs, the Dodgers were active on the free-agent market, signing starting pitchers Zack Greinke, a former Cy Young winner, and Ryu Hyun-jin, who had been an All-Star in each of his seven seasons in the Korea Baseball Organization from 2006-12. Greinke, who won the Cy Young with Kansas City in 2009, provided the Dodgers with what MLB.com called "unprecedented starting pitching depth."
On October 14, 2014, he was removed from his position as General Manager of the Dodgers after the Dodgers failed to advance to the World Series despite a 2014 opening day payroll more than $30 million higher than any other MLB team, and $55 million higher than any other National League team. Colletti remained with the team in a new position as Senior Adviser to the President. In addition, Colleti would be added to the Sportsnet LA broadcast team.
Colletti was a top front office executive – either an assistant general manager (AGM) or general manager (GM) – continuously from 1997 until 2014 with two clubs, the San Francisco Giants and Los Angeles Dodgers. Only five other GMs served continuously, either as an AGM or a GM, from 1997-2014. Of the six GMs who served continuously for the past 18 seasons as assistant general manager or general manager, only Brian Cashman of the New York Yankees had a higher winning percentage.
Colletti is active in several community and charity efforts in Los Angeles.
He and the Dodgers have partnered with Guide Dogs of America to sponsor lifelong working partners for the visually impaired. In October 2011, Colletti joined radio personality Peter Tilden and Colletti's fri ends from the band Chicago, who played a benefit concert that raised funds for Guide Dogs of America and the Foundation for Fighting Blindness.
Colletti received a prestigious Humanitarian Award from A Place Called Home, located in South Central Los Angeles, which provides at-risk youth with a secure, positive environment. The Los Angeles City College Foundation also honored Colletti for his work with youth. On October 23, 2012, the Los Angeles City College Foundation honored Colletti for his work with youth.
Vicki Santo, widow of Cubs' Hall of Fame legend Ron Santo, and Colletti established a foundation RonSantoFoundation.com to place service dogs with people suffering from diabetes. The dogs are trained to alert their human partners when their blood sugar is low, helping prevent sudden, unexpected onsets of hypoglycemia that can be devastating.
Actors Tim Robbins and Helen Mirren worked with Colletti to raise more than $100,000 from 2011 to 2013 for Get Lit, a city program designed to provide youth with opportunities to develop an appreciation for literature, writing, reading and poetry.
As an advisory board member of Vision To Learn, Colletti works with the organization founded by Austin Beutner to provide eye examinations and free glasses to poverty-stricken, urban youth in some of the hardest-to-reach communities. Vision To Learn has screened more than 120,000 kids in Los Angeles and Sacramento, provided over 20,000 with eye exams and more than 16,000 with free glasses.