Johnson has been married to Gralin Jerald since 1982, with whom she has a daughter, Danyel
Jerald began her career with small guest roles, appearing in The Paper Chase from 1984 to 1986, General Hospital in 1986, and Do The Right Thing in 1989 before playing the title character's unflappable personal assistant, Beverly Barnes, on The Larry Sanders Show. Throughout the 1990s, Jerald guest starred in several television series, including Parker Lewis Can't Lose, Star Trek: The Next Generation, Grace Under Fire, Cosby and Family Law.
Jerald also teaches acting workshops and produces and directs for Outreach Christian Theater Company, which she and her musician husband Gralin Jerald founded in 1994.
Following Larry Sanders, Jerald appeared in the 1997 film Absolute Power and Star Trek: Deep Space Nine playing freighter captain Kasidy Yates, the love interest for the series' main character Benjamin Sisko, a recurring role which she played from 1995 to the show's end in 1999. She also had a recurring guest role on ER as Lynette Evans from 1998 to 1999. She then appeared as Roscoe Dellums in the Emmy Award winning TV movie The Color of Friendship. Jerald also guest starred on Frasier, The Practice, Touched by an Angel and The X-Files.
Jerald's arguably most-recognized role came in 2001 when she appeared in the pilot episode of the Kiefer Sutherland-led Fox series, 24, playing Sherry Palmer, the wife of Senator David Palmer. She appeared in all but two of the first season episodes and multiple episodes of the second and third seasons.
In 2003, Jerald played Condoleezza Rice in DC 9/11: Time of Crisis, a TV movie about the September 11 attacks in 2001. She reprised the role in the miniseries The Path to 9/11, which aired September 10–11, 2006.
Jerald joined the cast of ABC's Castle in its fourth season as the new captain of the 12th Precinct, Victoria "Iron" Gates, replacing Ruben Santiago-Hudson's deceased character Roy Montgomery as captain of the precinct.