Kristina Apgar was born in Morristown, New Jersey. She began dancing at an early age with the New Jersey Ballet Company.
Apgar was a model with the Wilhelmina Models Agency. Clients included Delia's, Clean and Clear and Abercrombie and Fitch.
Her first television appearance was on the daytime soap As the World Turns. From there she went on to a recurring role on New York based show Rescue Me, with Denis Leary and guest starred on Law & Order: Criminal Intent. Upon arriving in Los Angeles, Apgar recurred on Terminator: The Sarah Connor Chronicles. From 2008-2009, Apgar was a series regular on The CW's drama Privileged, playing Lily Smith, Megan Smith's estranged sister (played by Joanna Garcia).
In 2011, Apgar had a recurring role on Detroit 187 on ABC playing Riley Sullivan, Detective Stone's (D.J. Cotrona) troubled ex-girlfriend. She also was a lead guest star on CSI: Miami with David Caruso playing Monica Dow/Alexis Taymor. In the Fall of 2011, Apgar guest starred on It's Always Sunny in Philadelphia and recurred on the CW's 90210 as Jane, a new love interest for Liam Court (Matt Lanter).
In 2012, Apgar guest starred on The Mentalist on CBS playing Lindy Hayes, a troubled, young girl who has begun turning tricks.