Harriell, last seen on Broadway in In the Heights, will play Marta Rodriguez, a new nurse on the floor and a mother of three who takes extra shifts when she can. Chestnut, who will have a season-long arc, will play Ike Prentiss, a new trauma doctor who was a former army medic.
Harriell was also seen on Broadway in Lennon and Rent.
"Nurse Jackie" stars Edie Falco, who was last seen on Broadway in The House of Blue Leaves. The series will return to Showtime for a fifth season in 2013.