[3][4] Eddie Casiano was born in Manhattan, New York City to Puerto Rican parents.

[5] Casiano and Nelson Quiñones were teenagers at the time (fifteen and seventeen, respectively) and hadn't finished high school yet, when they were signed by the Atleticos de San German BSN team.

In 1991, with the departures of Bobby Ríos and Ernesto Malcolm from San Germán, Casiano and Quiñones became starters with 18 and 20 years respectively.

During this time, Casiano also participated in his first Olympic Games, joining Atleticos teammate Jose Ortiz as a member of the Puerto Rican National Basketball Team.

After the 2000 season, Casiano was traded to the Leones de Ponce along with Bobby Joe Hatton and Carlos Cortés.