She completed her school level education from the Highlands Ranch High School, Colorado. She started her professional career in 1991 by working as a cast member of the Mickey Mouse Club. She worked on the show for three years and quit the show in 1994. After she left the show, she, along with another cast of the show such as Britney Spears, Christina Aguilera, Justin Timberlake, JC Chasez, and Tony Lucca. recorded an album titled MMC. She relocated to Los Angeles to start her acting career. She starred with petty roles in several films and television shows and by starring in Aaron Spelling's Malibu Shores in 1996 earned her some recognition.
Keri's career-defining role came as "Felicity Porter" in the popular WB's series called Felicity in 1998. For her splendid performance, Keri won her maiden Golden Globe award in 1990. She remained with the show until its conclusion in 2002. Upon completion of the series, Keri starred alongside Mel Gibson in the film We Were Soldiers in 2002 and opposite Joan Allen in the film The Upside of Anger in 2005. Keri made her Broadway debut in the year 2004 with the show "Fat Pig" alongside Jeremy Piven and Andrew McCarthy.
Russell starred in the sequel of movie Rise of the Planet of the Apes titled Dawn of the Planet of the Apes in 2014. She was cast alongside actors Gary Oldman and Andy Serkis.