In 2003, he participated in the State Assembly's internship program, where he was assigned to work with Assemblyman Rubén Díaz Jr. Crespo earned his B.A.

Crespo also spent three years living in Lima, Perú, where he completed fourth and fifth grades while attending Santa Tersesita.

In the Assembly, Crespo authored an anti-fraud bill to protect immigrants that passed both houses of the legislature and worked to expand legal services to underserved communities outside New York City.

In the Bronx, Crespo has pushed for Metro-North Railroad service that will cut commuting time into Manhattan by an hour and worked on improving traffic congestion and air quality for the neighborhoods near Hunts Point Terminal Market by building an additional ramp to the Bruckner Expressway, thereby removing hundreds of trucks from local roads.

[5] In 2020 after 11 years as a member of the New York State Assembly Marcos Crespo joined Montefiore Medical Center in The Bronx where he was named Senior Vice President, Community Affairs.