 In 2002, Diaz was elected to the New York State Senate.He represented the 32nd district in the New York State Senate from 2003 to 2017; his Senate district included parts of the Bronx neighborhoods of Castle Hill, Parkchester, Morrisania, Hunts Point, Melrose, Longwood, and Soundview.In 2007, Díaz expressed anger at Governor Eliot Spitzer after Spitzer reversed course and abandoned his plan to allow illegal immigrants to obtain New York driver's licenses.