Chalmers turned professional in 1995 and made a strong start to his professional career, winning four times in Australia in the next few years, including the 1998 Australian Open. In 2011, Chalmers held off John Senden and Tiger Woods to win the Australian Open for the second time, 13 years after he won his first. He followed this up with a win at the Australian PGA Championship, to take the second Australian major of the year. He defeated Robert Allenby and Marcus Fraser in a sudden death playoff to take the title. These wins led him to win the 2011 PGA Tour of Australasia Order of Merit.
- 1998: Finished fourth at the PGA Tour's Qualifying school to win a PGA Tour card for 1999
- Chalmers' best PGA Tour finish is second at the 2000 Kemper Insurance Open and at the 2009 Buick Open
- 2011: Attempted to be only the second player ever to win the Australian 'triple crown' in a single season.
- Won the 2011 PGA Tour of Australasia Order of Merit.