Peek entered the PBA in 1998 after being drafted third overall by the now-defunct Pop Cola Panthers. Because of his height, standing only at 6 ft 4, despite his perceived presence in the low post as a top player in the PBA and judging by his stats, he remains not to be selected by the Philippine national team. He was the Panther's leading scorer, rebounder and shot-blocker. At the start of the 2001 PBA season, he was traded along with Jon Ordonio, to the rebuilding Alaska Aces for then-Alaska franchise playerJohnny Abarrientos and Poch Junio. During his time with the Aces, Peek's career blossomed despite the team falling short of winning a championship. In his first two years with the Aces, Alaska's decision to go "younger" paid off. Surrounded by talented youngsters John Arigo, Mike Cortez and Brandon Cablay during the 2003-04 Season, Peek won Best Player of the Conference honors in the 2003 Invitational Cup including a championship against his former team which is, during that time, named the Coca-Cola Tigers. He was also included in the Mythical first team twice. During the third conference of the 2004-05 Season, Peek was traded back along with John Arigo to his former team, the Coca-Cola Tigers in exchange for former Alaska player Jeffrey Cariaso and Reynel Hugnatan. In the 2007-08 Season, the Tigers traded Peek and a first round draft pick to Talk N Text in exchange for disgruntled star Asi Taulava. Before the 2010-11 PBA Season ended, the Sta.Lucia Realtors announced that the team had been put on sale and Peek was dealt to the Realtors in a controversial trade that involved Sta. Lucia stars Kelly Williams and Ryan Reyes. Peek played the few remaining games in Sta. Lucia before going back to Talk N Text at the start of the 2010-11 PBA Season. On November 7, 2011, Peek was shot in the neck by an unidentified gunman at the parking lot of the RFM Sports Center in Pioneer in Mandaluyong City. He was rushed to the hospital and was out of danger. He has since returned to active play from the incident. On February 26, 2014, Ali Peek announced on Twitter his retirement from the PBA. Peek played for about 16 years in the league. He currently works as a color commentator in the league.