She was found early on Friday morning outside her apartment on Forrest Street, West Australian Police say.
Police said no criminality was involved but investigations by the police coronial unit continued.
Tarvydas closed her boutique on King Street in 2012 due to high rents, but her flagship store in Claremont remained.
A year later, her business went into liquidation, despite her list of high profile clients including Rihanna, Elle Macpherson, Emma Watson, Jennifer Hawkins and Natalie Bassingthwaite.
She also designed the now-famous plunging red backless gown worn by Rebecca Twigley, model and then girlfriend of West Coast Eagle Chris Judd, at 2004’s Brownlow Medal ceremony.
Tarvydas’ admirers took to social media to pay tribute, with Perth Fashion Festival saying they had lost a “a truly wonderful designer and friend”.
Fellow Perth fashion designer Aurelio Costarella said he was devastated.
It was a very sad day for the industry and anyone who knew her, Costarella said.
“Rest in peace my friend X,” he tweeted.
Tarvydas founded the business in 1970 when she was a teenager.