March, 36, played ADA Alexandra Cabot for seven seasons and Neal, 34, portrayed ADA Casey Novak for six. It is not yet known how many episodes each actress will appear in.
Last season's two primary ADAs were played by Melissa Sagemiller and Christine Lahti. However, Lahti's character was killed in episode 17 and Neal returned in the spring for a cross-over episode with Law & Order: LA. March last appeared on the procedural in Season 11.
The actresses' return amid a major cast upheaval for the last remaining Law & Order spin-off. Christopher Meloni recently announced he would not come back to the show, just as his on-screen partner, Mariska Hargitay, prepares to return in a reduced capacity. Her character, Detective Olivia Benson, will be promoted to Captain this upcoming season.
NBC and Wolf Films announced last week that Chase star Kelli Giddish and Cold Case's Danny Pino will join SVU as the new detective team. Series veterans Ice-T and Richard Belzer will also reprise their roles this season.
Law & Order: SVU is set to begin production on the new season later this month. The series airs Wednesdays at 10/9c on NBC.