Mansouri realized that he did not have the obsessive dedication necessary for a vocal career. After his father refused to subsidize his musical studies any longer, he found a job to support his studies and in 1960, became an American citizen. After receiving a B.A. degree in psychology, he saw his first complete opera performance, Madama Butterfly, at the Hollywood Bowl-an experience that changed the direction of his career. When San Francisco Opera toured to Los Angeles, Mansouri performed as a supernumerary, making his "Company debut" as a soldier in Otello.

While still studying voice, Mansouri met his future wife, Marjorie Thompson, in 1952 and married her in 1954. Their daughter, Shireen, was born in 1967.