High Court Justice Colin Birss ruled in favor of the singer on Wednesday, saying buyers were likely deceived by believing Rihanna had authorized its sale.
"I am quite satisfied that many fans of Rihanna regard her endorsement as important," the judge said in his ruling. "She is their style icon. Many will buy a product because they think she has approved of it. Others will wish to buy it because of the value of the perceived authorization itself. In both cases they will have been deceived."
Birss also said the sales caused a loss of control over Rihanna's reputation in the fashion realm, where the singer has been trying to carve out a name as a designer. She has a clothing line in her name at a rival store.
The shirts were first sold as the "Rihanna Tank." After her complaints, they were sold as being the "Headscarf Girl Tank" and the "Icon Tank."
Topshop's owner, Arcadia Group Brands Ltd., had argued that Rihanna was seeking legal recognition for a flawed assumption that only a celebrity could market a product bearing his or her image.
Topshop said it was surprised and disappointed by the ruling and was considering an appeal.
"There was no intention by Topshop to create the appearance of an endorsement or promotion," it said in a statement. "We do not believe it conveyed any false message to our customers."
The judge did not make an assessment of damages in his ruling.