Benanti will play Detective Nick Amaro's (Danny Pino) wife, Leanne. When her character returns from overseas, she must figure out where her relationship stands.
The actress is set for a three-episode arc, which will begin with "Spiraling Down," set to air in December.
Benanti won the Tony Award in 2008 for her performance in Gypsy. She was also nominated for her performances in Swing!, Into the Woods and Women on the Verge of a Nervous Breakdown. The performer has also been seen on Broadway in The Sound of Music, Nine, The Violet Hour, The Wedding Singer and In the Next Room.
"Law & Order: SVU" airs Wednesday nights at 10 PM ET on NBC.