Toward the end of his training Viglielmo responded to an appeal for enlisting in a Japanese language program being conducted under the auspices of the ASTP (the word "Reserve" no longer applied).
After the end of the war in August 1945, his training was then directed toward being an interpreter during the Occupation of Japan, and he served as such in the 720th Military Police Battalion in Tokyo from April to September 1946.
He was accepted into the Harvard graduate program for Fall 1948, but chose instead to go to Japan for a three-year position teaching English as a foreign language at Meiji Gakuin University in Tokyo.
In 1971 Viglielmo translated the Sōseki novel Meian (Light and Darkness, 1916), which received high praise from Western literary critics such as Fredric Jameson and Susan Sontag.
Two years earlier, in 1969, he translated a brace of essays, The Existence and Discovery of Beauty, which the first Japanese Nobel Prize recipient Kawabata Yasunari gave in the form of public lectures as a visiting professor at the University of Hawai‘i in May 1969.
From the late 1950s on, Viglielmo also developed an interest in modern Japanese philosophy, introducing to the Western world works by the two principal figures of the Kyoto school, Nishida Kitarō and Tanabe Hajime.
He formed friendships with the bundan (literary establishment), including Mishima Yukio, Kenzaburō Ōe, Sei Ito, Satō Haruo, and prominent critics such as Okuno Takeo and Saeki Shōichi.
Viglielmo also developed a close connection with the Japanese anti-nuclear group Gensuikin (Congress for the Abolition of Atomic and Hydrogen Bombs), and especially with the Nagasaki branch.