Denman qualified for her first international team at the Australian Championships in 1996, after winning the 100-metre breaststroke.
At the 1996 Summer Olympics in Atlanta, Denman placed 11th in the 100-metre breaststroke, but fellow Australian Samantha Riley won the bronze medal. This meant that Denman swum the breaststroke leg in the heats of the 4×100-metre medley relay, before being replaced by Riley in the team that trailed the United States team home in the final.
Competing in front of a partisan home crowd at the 1998 World Championships in Perth, Denman set a personal best in winning silver in the 100-metre breaststroke, pushing American Kristy Kowal to within an arm's length. She also combined with Meredith Smith, Petria Thomas and Susie O'Neill in the final of the 4×100-metre medley relay to claim silver behind the Americans.
At the 1998 Commonwealth Games in Kuala Lumpur, Malaysia, Denman claimed gold in the 100 m breaststroke and the 4×100-metre medley relay. In 1999 she was omitted from the Australian national team, and in 2000 she made an unsuccessful attempt to qualify for the 2000 Summer Olympics in Sydney.
