In the summer of 2010, DeLeon took part in and scored in the U.S. Open Cup with Phoenix-based NPSL team Arizona Sahuaros.

DeLeon had a successful first season with the Cardinals, starting all 24 games and scoring 8 goals and 3 assists, and was named to the All-Big East first team.

[4] The Cardinals won the 2010 Big East Soccer Tournament[5] and advanced to the final of the 2010 College Cup, where they fell 1–0 to the Akron Zips.

In DeLeon's senior season at Louisville, he again started every game, scoring 6 goals and 6 assists, and was again named to the All-Big East first team.

DeLeon signed with Major League Soccer on December 29, 2011, and was chosen with the 7th overall pick of the 2012 MLS SuperDraft by D.C.

In the post-season, DeLeon was voted runner-up for the 2012 MLS Rookie of the Year award, losing out to fellow University of Louisville alum Austin Berry of the Chicago Fire.

[14][15] Born in the United States, DeLeon is also eligible to represent Trinidad and Tobago through his father, a former Trinidadian international.

[16] In January 2013, DeLeon was called up for Trinidad and Tobago's senior friendly against Peru on February 6, 2013,[17] but once again declined.

[18] In January 2016, DeLeon's father told Trinidadian media that his son was ready to play for Trinidad and Tobago and was working on acquiring a passport for the country.

[19] Nick is the son of Trinidadian international[16] and NASL player Leroy DeLeon, who played with the Washington Diplomats in the 1970s.

[citation needed] In March 2021, DeLeon stated his opposition to modern medicine by telling Toronto Sun reporter Steve Buffery "I’ve never had vaccines.