Jackson was born in Washington D.C. as Kellie Shanygne Williams. After Family Matters, she began acting in the ABC television show What About Joan. In 2006, Williams reunited with her former Family Matters co-star Darius McCrary on the UPN sitcom Eve for two episodes “Separate, But Unequal” and the final cliffhanger episode “Daughter Don’t Preach” as Lynn. She was also on the Style Network program Clean House for six episodes in 2009, as a substitute host for Niecy Nash.

In 2007 Jackson created the Kellie Williams Program with co-creator Jeff Rawluk in the Washington, D.C., area. The program will provide Washington, D.C., students between the ages of 14 and 20 an opportunity to produce a television show to air on Comcast Cable Local On-Demand. She stated, “I wanted to create a program similar to the one I grew up with (Howard University Children’s Theatre). I wanted to bring it to the masses, not to just people who were familiar with the arts but to people who had never experienced any art.”

Williams wed Hannibal Jackson on September 5, 2009 at Ebenezer African Methodist Episcopal Church in Fort Washington, Maryland. The two met in 2007, through a mutual friend. They have two children together, daughter Hannah Belle Jackson (b. 2010) and son John Ervin Jackson (b. 2012).