Holt was born in Brisbane, Queensland, Australia. She graduated from Stuartholme School in Toowong at the end of 2005. She is involved in several sports: swimming, volleyball, water polo, and Tae-Kwon-Do, in which she has a black belt. When she was younger, she was in the school choir.
Holt became engaged to longtime boyfriend Matt Kaplan in July 2015. The two got married in April 2016.
Holt is best known for her roles as Emma Gilbert in H2O: Just Add Water, Chastity Meyer in the Mean Girls 2, Samara Cook in Pretty Little Liars, as well as her most notable and recent role of Rebekah Mikaelson in CW hit series The Vampire Diaries, and it's spin-off The Originals.
In 2015, Holt was linked to CBS' Supergirl although she chose not pursue it. She starred in NBC "event series" Aquarius as Charmain Tully.