Lyndsy Marie Fonseca was born in Oakland, California, and spent her early years in Alameda and Moraga, California. Her early life was marked by a passion for dance, as she competed in the International Modeling & Talent Association, where she was recognized as the second runner-up for "Young Miss Dancer of the Year" and the first runner-up for "Miss Barbizon Young Miss Talent of the Year".
This early success caught the attention of a manager and agent, who discovered her and immediately helped her move to Los Angeles for her first pilot season at the age of 13. Her breakthrough role came when she landed the part of "Colleen Carlton" on the CBS soap opera, The Young and the Restless, a role she played for three years.
After leaving Y&R, Lyndsy expanded her horizons by landing guest appearances on shows such as Boston Public, CSI: Crime Scene Investigation, and House, among others. She also had recurring roles on the hit series Desperate Housewives, opposite Andrea Bowen and Nathan Fillion, and Big Love, as well as the hit comedy How I Met Your Mother.
In addition to her television work, Lyndsy has also had success on the big screen, with film credits including The Ward, Hot Tub Time Machine, Fort McCoy, and the smash hit Kick-Ass, in which she starred opposite Aaron Taylor-Johnson.
Recently, Lyndsy completed filming the two-hour Lifetime movie Five, which consists of five short films about breast cancer, directed by Jennifer Aniston, Demi Moore, and Penelope Spheeris. She is now starring as "Alex" in The CW's Nikita, playing the role of Alex, Nikita's former partner who plans to take down her old ally while also seeking revenge on the man who killed her family, airing on Friday nights at 8p.m. Eastern.
In her personal life, Lyndsy is the older sister of Hannah Leigh, who is also pursuing a career in acting, following in her footsteps.