The label will sell its final Summer 24 collection and wind up the business in mid-2025, Sylvester and partner and co-founder Wayne Conway have announced.
"We want to go out the way we came into this business, still loving what we do and being truly happy to do it", they said.
Sylvester began her career hand sewing screen-printed t-shirts with a punk rock edge.
The Massey fashion design alumni advertised her first streetwear brand Sister via graffiti on the streets of Auckland.
"We started this company with literally nothing more than wild faith in each other and a dream to create clothes that people would wear and love," the pair said in a joint statement.
"Since the day we opened the doors on that first store in Kitchener Street we have worked incredibly hard for three decades. And now we need to move on to a new chapter in our lives."
Sylvester has shown her designs at iD Dunedin Fashion Week and has been a judge for its International Emerging Designer Awards.