Long attended the Roman Catholic school St. Mary’s Academy in Inglewood, California. She was bused from South Los Angeles to Paseo Del Rey Elementary School in Playa Del Rey from 3rd grade through 6th grade. In addition to her academic classes, she studied ballet, tap, jazz, gymnastics, guitar, and acting. She graduated from Westchester High School in Los Angeles in 1989.

In 2000, Long was offered the role of Alex Munday in Charlie’s Angels, but she turned it down, and the role was eventually given to Lucy Liu. In 2003, she joined the cast of the drama Third Watch, where she played NYPD Officer Sasha Monroe, continuing until the series finale in 2005. In 2005 and 2006, Long appeared on Everwood, and appeared on Boston Legal during its 2006–2007 season. Long also starred in Big Shots from 2007–2008 alongside Michael Vartan and Dylan McDermott. In 2016, Long was cast in a recurring role for the TV series Empire. She acquired the role of Giuliana, a Las Vegas club owner.

Long appears in the video for Kanye West’s “Touch the Sky”. She directed Yolanda Adams’s music video for “This Too Shall Pass”. She won a NAACP Image Award for Outstanding Actress in a Drama Series in 2004 for her performance on Third Watch. Long co-directed and appeared in Ashanti’s music video, “Baby”. She also made a guest appearance on the sitcom Living Single during its first season.

Long started dating Ime Udoka in 2010 and they have a son born in 2011. The couple became engaged in May 2015. She also has another son, born in 2000, from a previous relationship with Massai Dorsey.

She appeared in the 2013 film The Best Man Holiday, reprising her role from the original 1999 film. Unlike the original film, however, her character is in an interracial relationship with a white man. Long was revealed to be pursuing an interracial relationship in the film and explained: “We’re living in a modern world where it happens and it’s OK and it’s no disrespect to any black man. I love black men, but the reality is the sistahs are marrying white men and the brothas are marrying white women and that’s the world that we live in and it’s not to be judged, and if it works for you then embrace it”. Director Malcolm D. Lee also supported the interracial relationship being portrayed in the film. “African-American women who are extremely successful can’t always find black male counterparts on that level so it’s a little bit of a reflection of reality that black women are starting to date outside their race — and why not?”

In July 2020, Long starred in the Netflix psychological thriller Fatal Affair.