In the United States she was allowed to enter Yale University's graduate program and completed it in record time. In 1943, at the age of 21, Cavaglieri received her Ph.D. in Organic Chemistry. The same year she married Victor Tesoro, with whom she would have two children.
Following her marriage, Giuliana Cavaglieri Tesoro worked summers for Calico Chemical Company before accepting a position as research chemist at Onyx Oil and Chemical Company in 1944. Here she was promoted to head of the organic synthesis department in 1946, assistant director of research in 1955, and associate director in 1957. She was then appointed assistant director of organic research for J.P. Stevens & Company. Late she moved to the Textile Research Institute for two years. In 1969, she accepted a position as senior chemist at Burlington Industries and was appointed director of chemical research in 1971.
In 1972 she accepted a post as Visiting Professor at the Massachusetts Institute of Technology, where she taught until 1976, remaining on the Faculty as adjunct professor and senior research scientist until 1982. She was then appointed research professor at Polytechnic Institute of New York University in Brooklyn, New York in 1982 and retired from there in 1996.
Tesoro made a number of advances in textile processing and organic compounds that improved textile performance for everyday consumers as well as efficiency for manufacturing systems. She developed flame-resistant fibers, designed ways to prevent static accumulation in synthetic fibers, and created improved permanent press properties for textiles.