Outside the United States, Martinelli appeared in Paris and Buenos Aires during his prime but – oddly enough – his native Italy did not hear him at his peak. In 1937, he returned to London to sing at the Covent Garden in highly acclaimed performances of "Otello" and as Calaf, opposite the exceptionally powerful English dramatic soprano Eva Turner. Martinelli retired from the stage in 1950, although he gave one final performance in 1967 – at the age of 81 – as Emperor Altoum in "Turandot", in Seattle. During retirement he taught singing in New York, where one of his pupils was tenor Jack Harrold.