He came to Tokyo intending to become a painter and studied under the famous Fujishima Takeji and Kuroda Seiki but had to give up an artistic career due to his father's sudden death.

Nishiwaki became interested in poetry while a student at Keio University, and contributed verses to the boy's magazine Shonen Sekai.

Nishiwaki then accepted a teaching post at Keiō University in April 1920, while continuing to contribute English verses to various journals, and editing poetry magazines on the side.

However, he arrived too late to be admitted to a university, and spent a year in London at ease, meeting with authors including John Collier and Sherard Vines.

Returning to Japan in 1926, Nishiwaki accepted a position as a professor at Keiō University's Faculty of Letters and taught the history of English Literature as well as a range of courses in linguistics.

He was one of the 14 poets arrested on charges of sedition, after the introduction of the National Mobilization Law as government censors chose to interpret some of his surrealistic poems in a critical manner.

During World War II, he evacuated to Chiba Prefecture with his library of over 3000 volumes, and later to back to his hometown of Ojiya in Niigata.

Nishiwaki also devoted effort to translation, publishing a Japanese version of T. S. Eliot's The Waste Land, which was received with great critical acclaim.

Nishiwaki was elected a Foreign Honorary Member of the American Academy of Arts and Sciences in 1974 and awarded the Order of the Sacred Treasure, 2nd class, by the Japanese government.