[1] Before his election to the Assembly, Heastie worked as a budget analyst for the New York City Comptroller.

[1] Heastie was first elected to the New York State Assembly in 2000 and represents the 83rd District, which covers the Williamsbridge, Wakefield, Edenwald, Eastchester, and Baychester sections of the Northeast Bronx.

He has also sponsored legislation to require mandatory reporting of alleged child abuse of students in New York City.

[2][3] In January 2015, Heastie's Assembly colleagues considered him a frontrunner to be elected Speaker, following the arrest of Sheldon Silver on federal corruption charges arising from an investigation led by U.S. Attorney Preet Bharara.

After his mother's death, Heastie ceased attempts to sell the home, having been advised by his lawyer that he was no longer obligated to do so; he later sold it for a profit of $200,000.