"Shockingly -- and I'm told this is not a joke -- we have ALSO won a primary in the neighboring 15th Congressional District via write-in campaign on the Reform line!" Ocasio-Cortez wrote on Twitter before going on to say she will reject the nomination and remain the Democratic nomination in the 14th district, which includes parts of the Bronx and Queens.
New York state law prevents candidates from running for two different offices simultaneously.
There were no candidates running on the Reform Party ticket in the 15th Congressional District, which was holding primaries and encouraging unaffiliated voters to submit their preferred candidates as a way to bring attention to what they say are broken election laws governing primaries in New York State, according to local news outlet City & State New York.
Ocasio-Cortez, now considered a rising star in the Democratic Party, gained national attention for unseating Crowley, once thought to be a potential Speaker of the House candidate to succeed Nancy Pelosi, by nearly 15 points in New York's June 26th primary election for federal offices.
Serrano has represented New York's 14th Congressional District since 1990, and was a New York State Assemblyman for 15 years prior to his service in the U.S. House.
The New York City Board of Elections did not immediately respond to ABC News' request for more information on Ocasio-Cortez's reported victory.
Ocasio-Cortez is expected to easily win election to the U.S. House in November, when she will face Republican Anthony Pappas, a professor at St. John's University. Hillary Clinton won New York's 14th Congressional District by 57 points in the 2016 presidential election.