As an amateur Dieppa represented Puerto Rico in international competitions, competing in the Light Flyweight division (– 48 kilograms).

[1] His second international participation of the year was in the Pan American Games that took place on Havana, Cuba.

[3] Dieppa debuted as a professional on February 13, 1993, when he fought Carlos Figueroa in an event organized at the Roberto Clemente Coliseum.

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.

On June 1, 1996, Dieppa won his first regional professional championship when he defeated Pablo Tiznado in a card that took place in Miami, Florida.

In this fight he won the Fecarbox Flyweight championship, a regional title sanctioned by the World Boxing Council.

Dieppa won three, non-title bouts in a row, including a unanimous decision in eight rounds against Kenny Berrios on June 7, 1997.

The World Boxing Organization considered stripping him of the championship, but decided that Dieppa was unable to defend the title due to matters outside of his control.

On March 20, 2004, Dieppa participated in his third title defense, against Colombia's Kermin Guardia in a fight held at the Mario Morales coliseum, in Guaynabo, Puerto Rico.

Dieppa's next defense took place on July 30, 2004, in a card organized in Louisville, Kentucky, where he fought against Ulises Solís.

On January 29, 2005, Dieppa fought against Alex Sánchez in a fight that took place at the Rubén Rodríguez Coliseum, in Bayamón, Puerto Rico.

On December 17, 2005, Dieppa returned to action versus Juan Alfonso Keb Baas in an event organized in Fajardo, Puerto Rico.

[8] Following this fight, Dieppa defeated former champion Alex Sanchez, and lost by unanimous decision to Iván Calderón for the WBO's championship.