Born in Gradara, in the Province of Pesaro and Urbino on the Adriatic Coast in 1935, the son of a railway attendant, Bruni started painting as a young boy. He was initially a pupil of Giuliano Vanghi; from 1953 to 1959 he attended the Art Institute in Pesaro. He then moved to London, where he became interested in pop art. In 1960, after an exhibit of his work at London's John Whibley Gallery, and after meeting a girl from Hamburg, he moved there to live with her and enrolled at the Hochschule für bildende Künste Hamburg. He has lived in the city ever since and visits his hometown regularly.
In the 1970s, Bruno Bruni made a name for himself as a draftsman, lithographer, painter and sculptor in the international art world. In 1977, he won the International Senefeld Competition for Lithography. He is influenced primarily by German expressionists like Otto Dix, George Grosz etc. and the Italian old masters . In particular, he is noted as one of the few lithographic artists "who paint all work directly onto the stone". He is especially known for his erotic female forms. He has said, "I cannot paint an abstract picture. If I had gone along with the trends I'd have disappeared long ago".He resides in a converted swimming pool, more than a century old, which serves as apartment, workplace and gallery. He sells his art through his wife's gallery in Hanover and is reputedly one of Germany's top earning artists. He is also a keen cook of Italian cuisine, and is a boxing fan and a close friend of former boxing champion Dariusz Michalczewski, for whom he used to cook for before matches. He has also cooked for Gerhard Schröder and has published a cooking book with his favourite recipes, memoirs and pictures related to his life.