Ralph's other notable roles include The Mighty Quinn (1989), Mistress (1992), The Distinguished Gentleman (1992), Sister Act 2: Back in the Habit (1993), and The Comeback Trail (2020).

During her time at Rutgers, Ralph was one of the earliest winners of the Irene Ryan Acting Scholarships awarded by the Kennedy Center American College Theater Festival.

Ralph began her career in the 1970s, starring in the 1977 American crime comedy film A Piece of the Action directed by Sidney Poitier.

[11] On television, she was in the cast of the CBS daytime soap opera Search for Tomorrow while starring on Broadway in Dreamgirls.

The following year, Ralph won the Independent Spirit Award for Best Supporting Female for her performance in the 1990 drama film To Sleep with Anger.

That same year, she played Etienne Toussaint-Bouvier on Designing Women, and co-starred with Eddie Murphy in The Distinguished Gentleman.

Her role as Dee Mitchell on Moesha (1996–2001) earned her five nominations for the NAACP Image Award for Outstanding Supporting Actress in a Comedy Series.

Ralph played a character who brought a new face to the sufferings of war in the NBC hit series ER.

Ralph's 2002 project Baby of the Family concerns a young child who is born with a caul over her head, which enables her to see ghosts and the future.

In 2013, Ralph appeared in the NBC television show Smash as Cynthia, the mother of Jennifer Hudson's character.

Some of her recent TV appearances include the TNT dramedy Claws, and on the Nickelodeon sitcom Instant Mom as the mother of Stephanie (Tia Mowry).

From January 10 to April 11, 2019, Ralph appeared as one of the main characters, Rose, in the television series Fam which ran for one season and was canceled in May 2019.

[17] In 2023, Ralph performed "Lift Every Voice and Sing", also known as the Black national anthem, at the Super Bowl LVII pre-show.

[22] In July 2004, Ralph was inducted as an honorary member of Delta Sigma Theta sorority at the 47th National Convention in Las Vegas, Nevada.