As of August 2016, he holds the Salvadoran records in the 100 meters, 200 meters, 400 meters, 800 meters and 1500 meters.
In 2016, Marcelo Acosta became the first swimmer from El Salvador to qualify for the Olympic Games with an "A" cut. At the third stop of the Arena Pro Series in Orlando, Acosta won the 1500m race with a time of 15:13.09.[3]
At the 2016 Olympic Games in Rio de Janeiro, Acosta finished 22nd in the 1500m freestyle with a new national record time of 15:08.17.
At the 2017 World Aquatics Championships, Acosta finished in 14th place in both the 800 m freestyle at 7:55.70 and the 1500m freestyle at 15:04:79.