Dieppa debuted as a professional on February 13, 1993, when he fought Carlos Figueroa in an event organized at the Roberto Clemente Coliseum. He won the fight by knockout in the first round. His first professional fight in Vieques took place on March 7, 1993, when he knocked out David Almodouvar in the second round. It took Dieppa almost eight months to return to a boxing ring in an official fight. This was his first major lay-off from boxing. He returned, on January 29, 1994, and participated in a boxing card that took place in San Juan, where he defeated Jose Hernandez by unanimous decision. Dieppa's first fight outside of Puerto Rico took place on April 13, 1995, when he fought Hipolito Saucedo, in Las Vegas, Nevada. The contest was scheduled for six rounds and the judges declared it a draw. Following this fight he participated in four fights organized in Ponce and San Juan, winning two by knockout.