He founded the consulting company Arthur D. Little and was instrumental in developing chemical engineering at the Massachusetts Institute of Technology (MIT).

He is credited with introducing the term unit operations to chemical engineering[2] and promoting the concept of industrial research.

In 1886, he joined Richmond Paper Company in East Providence, Rhode Island, as a chemist, later becoming superintendent of a paper mill,[8] and effectively recognised that the chemical engineering design was wrong: by correcting this, he came to his first patent.

Griffin and Little prepared a manuscript for The Chemistry of Paper-making which was for many years an authoritative text in the area.

[6] The partnership dissolved in 1905 when Walker dedicated his full-time to being in charge of the new Research Laboratory of Applied Chemistry at MIT.