Salas debuted playing for the Universidad de Chile in 1993. In 1994, he played overseas for the first time, sharing the bench with legendary player Hugo Sanchez, among others, with the Atlante first division team in Mexico. He finished his participation with Atlante in 1995. In 1996, Salas went on to play with River Plate of the Argentine first division. In 1998, he participated with Chile in the World Cup, after his run at River Plate was over.
Marcelo Salas scored 29 goals in 54 games at the Argentine league. With the Chilean national team, he has 21 goals in 27 games.