He transferred to Iona Preparatory School in New Rochelle, New York, which has a stronger baseball program.

[14] During the 2014–15 offseason, Minor League Baseball suspended Mazzilli for the first 50 games of the 2015 season for his second positive test for a "drug of abuse".

[16] In August 2016, the Mets promoted Mazzilli to the Las Vegas 51s of the Triple–A Pacific Coast League.

Mazzilli split the 2017 season between Binghamton and Las Vegas, batting a cumulative .254/.340/.362 with 5 home runs, 40 RBI, and 9 stolen bases in 110 contests.

[18] On April 10, 2018, the Mets traded Mazzilli to the New York Yankees in exchange for Kendall Coleman.

[21] On May 5, 2019, Mazzilli signed with the Long Island Ducks of the independent Atlantic League of Professional Baseball.

On December 9, 2019, Mazzilli signed a minor league deal with the Chicago White Sox.

[24] On April 13, 2021, Mazzilli signed with the Long Island Ducks of the Atlantic League of Professional Baseball.