Born in Mount Vernon, New York, Schawlow was educated at the University of Toronto and worked at Columbia (1949–51) and at the Bell Telephone Laboratories (1951–61). He became professor of physics at Stanford University in 1961, retiring in 1991.

Schawlow is noted for his work on the development and use of lasers. He collaborated with Charles Townes in early work on maser principles and is generally credited as a coinventor of the laser. Although he did not share in Townes's Nobel award (1964), Schawlow did share the 1981 Nobel Prize for physics with Nicholaas Bloembergen for their (independent) research in laser spectroscopy. In particular, Schawlow, with Theodor Hänsch, has used tunable dye lasers for high-resolution spectroscopy.