Was considered for a role in The Bad News Bears (1976), but lost it to Academy Award winner Tatum O'Neal.
Younger sister of Jimmy McNichol.
McNichol's role in the ABC Afterschool Specials (1972), ABC Afterschool Specials: The Pinballs (1977), was to advertise and promote the Halter Top fashions. She wore her personally designed halter tops on the show.
Her maternal grandfather was of Lebanese descent. Her other ancestry includes Scottish, Walloon-Belgian, German, and English.
Ranked #49 in VH1's list of the "100 Greatest Kid Stars"
Dropped out of acting because she was sick and tired of acting, wanted to have an average life, and one thing she pursued was going to school to learn how to style hair.
Longtime friends with Elisabeth Brooks and Kari Michaelsen.
Turned down the Jodie Foster role in Taxi Driver (1976).
Turned down the Brooke Shields role in Pretty Baby (1978), due to conflicts with Family (1976) producer Aaron Spelling.
Taught acting at a private school in Los Angeles. 
Announced her retirement from acting in 2001.
In January 2012, McNichol told People Magazine that she is a lesbian, and that she has lived with a romantic partner named Martie Allen since the early 1990s. McNichol said that she finally chose to come out of the closet to "try to help kids who are being bullied.".