The woman, whose first name is believed to be Taylor, collapsed and stopped breathing at Toronto's Molson Amphitheatre while attending the festival, reports Toronto Star.
She was rushed to a local Toronto hospital, but ultimately died soon after arriving for medical care. The woman was believed to be in her early 20s.
Paramore lead singer Williams is among many musicians who have offered their condolences to Taylor's family in the wake of the tragedy.
"My heart and prayers go out to family and friends of the young girl, Taylor, who passed away at Warped Tour today. Rest in peace," Williams tweeted.
The Swellers and Chelsea Grin also tweeted their own condolences on the woman's passing.
Warped Tour 2012 is expected to continue on Tuesday in Darien Centre, NY.