Warsaw officials asked that a naked breast be covered on a poster advertising the Miss World 2006 contest, the artist's agent said.
Artist Rafal Olbinski placed a white scarf with the "Miss World" inscription across the offending body part, said his agent, Piotr Reichel. He "agreed to make the change at the request from the Warsaw promotion office," the agent added.
This year's Miss World contest is to be held in the Polish capital on September 30.
The city's symbol is a naked-breasted mermaid. Olbinski's poster originally showed a mermaid on a seesaw, with her red top revealing one of her breasts.
The promotion office is overseen by Warsaw's conservative-run city hall. The acting mayor is former Prime Minister Kazimierz Marcinkiewicz, whose Law and Justice party supports conservative moral values.
Neither Olbinski, who lives in New York, nor the head of the promotion office were immediately available for comment.