At the 2004 Summer Olympics in Athens, Mularoni was elected by the Sammarinese National Olympic Committee (), as San Marino's top swimmer, to be the flag bearer in the opening ceremony. He qualified only for the men's 200 m freestyle by clearing a FINA B-standard entry time of 1:53.87 from GSSE in Valletta, Malta. He challenged seven other swimmers in heat three, including 16-year-old Shaune Fraser of the Cayman Islands. He rounded out the field to last place by a 3.16-second margin behind winner Aleksandar Malenko of Macedonia in 1:56.18. Mularoni failed to advance into the semifinals, as he placed fifty-sixth overall in the preliminaries.