Avgeropoulos was born on 17 June 1986 in Thunder Bay, Ontario to Greek parents. She grew up fishing, hunting and camping, spending most of her free time outdoors. She started playing drums when she was 16. After studying broadcast journalism for two years in her hometown, she moved to Europe. Several months later, she came back to Canada and settled in Vancouver. At the age of 20 she underwent surgery in order to remove a big tumour from her chest and throat, with her vocal cords being removed and put back in. This procedure affected her voice.

In 2010, Avgeropoulos was cast as Kim Rhodes in the film Hunt to Kill, which became her break-out role.

Early in 2013, Avgeropoulos made her break-out in television after being cast for a recurring role in The CW’s Cult. However, the series failed to attract viewers and after episode 7, the show was cancelled. The remaining six episodes of the show were broadcast later in the summer.

In late 2018, Avgeropoulos was involved in a domestic violence incident when she and her boyfriend allegedly began arguing in a car on the Ventura (134) Freeway shortly after midnight on 5 August 2018. Avgeropoulos was on new medication mixed with alcohol, and was accused of striking him multiple times in the head, neck and arm, resulting in minor injuries according to the District Attorney’s Office. She was then charged with domestic violence. Avgeropoulos’s boyfriend wanted the charges dropped and stated that she doesn’t pose a threat. The case was formally dismissed with all charges dropped, as there was no intent of harm on Avgeropoulos’ part, but rather “an adverse reaction to medication that triggered the outburst.”