In 1973, Feldshuh appeared on television in a supporting role in Scream, Pretty Peggy. In 1976, she also had a supporting role in Ryan's Hope, and in the following year, 1977, she played Katharine Hepburn in The Amazing Howard Hughes. However, Feldshuh came to international prominence as Helena Slomova in the 1978 mini-series Holocaust, based on Gerald Green's novel. Between 1991 and 2007, Feldshuh had a recurring role as defense attorney Danielle Melnick on Law & Order.

Feldshuh married New York attorney Andrew Harris Levy in 1977. Actress Ruth Gordon was her maid of honor. They have a son, Garson, an Economist and graduate of Harvard and Oxford universities; and a daughter, Amanda, who graduated from MIT. When Amanda married in 2014, Feldshuh gave her the advice, “You know how to have a successful marriage? Shut one eye, and don't leave. Some of it's fun and some of it isn't. It can be challenging, but you do not leave the field of play.” Her nephew, Noah Feldshuh, is a member of alternative rock band X Ambassadors.

Feldshuh appeared on the stage under the name "Terri Fairchild" before deciding to incorporate her Hebrew name and her original surname as her professional name, Tovah Feldshuh. She said of her name changes: "I fell in love with a Christian boy, Michael Fairchild, who didn't want to kiss a Terri Sue. He said: 'Terri Sue doesn't fit you at all. What's that other name of yours? Tovah? Now that's a name!" In 1994, she joked that she could have changed her name to "Goody Two-Shoes," since "Tovah" is Hebrew for "good," while "Feldshuh" translates from German as "field shoe."

Feldshuh made her cabaret debut at the Algonquin Hotel Oak Room with her act, Tovah: Crossovah! From Broadway to Cabaret, which was followed by Tovah: Out of Her Mind! She took the latter show on the road to Philadelphia, Houston, Dallas, San Francisco, Los Angeles, Chicago, Hong Kong, and Sydney. The West End production sold out an eight-week run at the Duke of York's Theatre. The Boston Globe selected her as "Best Cabaret Artist of 2000." In 2000, she co-wrote and performed in a one-woman play about Actress Tallulah Bankhead titled Tallulah Hallelujah!

For her charity work, she is the recipient of the Eleanor Roosevelt Humanities Award, Hadassah's Myrtle Wreath, and the Israel Peace Medal. The National Foundation for Jewish Culture honored her with the 2002 Jewish Image Award and the Performing Arts award in 2006.

Feldshuh's feature film appearances have included Lady in the Water, The Triangle Factory Fire Scandal, A Walk on the Moon, Happy Accidents, Brewster's Millions, The Idolmaker, The Blue Iguana, A Day in October, The Believer, Love Comes Lately, Just My Luck, and Kissing Jessica Stein. She also appeared as Ruthie in the 2004 film The Tollbooth.

Other Broadway credits include Saravà, Lend Me a Tenor, and Golda's Balcony, william Gibson's work about the late Israeli Prime Minister Golda Meir. Golda's Balcony set a record as the longest-running one-woman play in Broadway history on January 2, 2005.

Feldshuh appeared in Goyband, co-starring Adam Pascal, Amy Davidson, Cris Judd, Dean Edwards, Tibor Feldman and Natasha Lyonne. She was also slated to star in the psychological thriller Acts of Mercy. In 2009, Feldshuh recorded the song "Bein Nahar Prat" for the organization Pioneers For A Cure, with the proceeds benefiting Ellen's Run.

In 2012, she appeared as Mossad agent Rivka in the Covert Affairs episode "Wishful Beginnings". In 2014 she appeared in the film She's Funny That Way.

It was announced at the September 21, 2013, Broadway performance of Pippin that Andrea Martin's last performance as Berthe (Pippin's grandmother) would be the following day and that Feldshuh would be subsequently taking over the role. In 2014, she starred in Gypsy at the Bristol Riverside Theatre as Mama Rose.

In March 2015, Feldshuh hiked Mt. Kilimanjaro with her son. She told Variety she was inspired after the 2014 death of her mother at age 103, and her own athletic role in Pippin, in which she had to swing on a trapeze. "I really do feel we're only in this body once," she said. "I just want enough money to buy experience. I can forego a dress, but the idea of taking a trip and trekking Mt. Kilimanjaro, or going on the Trans-Siberian railroad, or tracking lemurs in Madagascar — these things are very exciting to me. To see the world until I leave my own body. It’s now or not at all."