The animal rights organisation People for the Ethical Treatment of Animals (PETA) claims more than 140 international retailers had dropped mohair following its video depicting the maltreatment of goats killed for mohair.
"We've updated our animal welfare policy," ASOS told AFP in an email, saying it would "no longer be stocking" products containing silk, feathers and down, bone, teeth or shell (including mother-of-pearl), cashmere and mohair.
The changes mean third party products are brought into line with existing rules for own-label ASOS design products, and add silk, cashmere and mohair to the policy.
No further orders will be placed for products containing these materials and the site will be free of these materials by the end of January 2019, ASOS said.
The brand, which boasts 12.4 million active customers worldwide, had already banned products containing fur or materials from threatened or endangered species.
"PETA applauds ASOS for leading the charge for compassion in fashion," says its corporate projects director Yvonne Taylor.
"In response to PETA's campaigns, consumers are changing the face of the industry by demanding that designers and retailers ditch animal-derived materials in favour of cruelty-free alternatives that look great without causing suffering."
H and M, Gap, Zara and Topshop announced in May that they were turning away from mohair after PETA's video shot in South Africa.
In the footage, Angora goats -- whose wool is used to make sweaters, scarves or blankets -- are dragged by the horns and legs, pulled by the tail and thrown on the ground by shearers.