The British designer, who grew up on an organic farm, unveiled an autumn-winter collection Thursday that was heavy on chunky knitwear, with accessories that included pink satin stilettos and large rubberized canvas bags.
Like her late mother Linda, McCartney is a prominent animal rights activist. She is the only top-tier designer who has steadfastly refused to use leather or fur, a difficult stance in an industry that relies on high-margin accessories for the bulk of its profits.
McCartney said she supported militants who disrupted two fashion shows on Wednesday to protest against the use of animal pelts.
"I totally disagree with any electrocuted animals on people's backs, so I think it's for the right reasons," she told reporters.
The designer wore her heart of her sleeve with Fair Isle sweaters patterned with a polar bear motif. She provided luxurious alternatives to fur with a cocoon-shaped coat in tufted gray wool and a zippered maxi-cardigan covered in curly black wool.
"It's sort of giving more staples hopefully of every woman's wardrobe, but really getting it completely right and fine-tuning it down to the minimum, but also with little details and high luxury fabrics and finishing," McCartney said.
Daywear included cashmere all-in-ones with racer backs in black or eye-popping pink. Party girls had a choice between pearl satin shifts or a black baby doll nonchalantly paired with a hooded anorak.
Ethical fashion is going from strength to strength, reflecting strong consumer demand for fashion with a conscience, noted Matilda Lee, editor of the lifestyle section of British magazine The Ecologist.
"Stella McCartney is a pioneer. She's fabulous on a lot of fronts because she has combined the high-end designer aspect of it with staying true to her ethical standpoint," said Lee, who produced a guide to ethical fashion for London Fashion Week.
The term spans everything from the use of recycled materials and organic textiles to socially responsible manufacturing that guarantees farmers a decent revenue.
Even big corporations are buying into the concept, helping to give the worthy-but-drab image of "green" fashion a major makeover. Think hip, rather than hippie.
As a result, demand for organic cotton is outstripping supply, with everyone from British high street retailer Marks & Spencer to denim brand Levi's seeking a share of the market.
Fledgling Norwegian brand FIN Fashion has secured organic Fairtrade-certified cotton from India for its fashion-forward designs, but it aims to compete on a par with mainstream brands.
"Our focus is to be a fashion brand with a distinct Scandinavian design, and on top of this it's organic and it's Fairtrade," said founding partner Eivind Pytte Odegard.
"For the ethical business to succeed, I think it's also very important that you actually make products that people will like because it's a good product, not just because it's ethical," he said.
The response to its first collection has been overwhelming, Odegard said. "Some people, whom you might call conscious consumers, have been looking for this for years now," he noted.
The cosmetics industry has also embraced natural products from niche brands like France's Themis, which uses ingredients produced by small cooperatives in developing countries.
McCartney is taking the movement mainstream with the launch of the first organic luxury skincare line, Care by Stella McCartney. The products carry the Ecocert organic quality label, contain no chemical preservatives and are not tested on animals, reports AP.
The Ecologists Lee said that, although such moves were positive, consumers needed to reduce their overall consumption patterns to really have an impact.
"People need to shop smart, and I think part of that is buying fewer clothes that are made to last and that can wear season after season, and part of that is looking into these designers that are pioneering a new sustainable fashion industry," she said.