Robertson first worked as a lawyer in Texas, but he left his profession for a sudden interest in acting[1] after being encouraged to do so by Joseph Jefferson.

[3] Robertson played supporting roles in many Hollywood films from 1930 until the year he died, typically portraying men of authority such as doctors, elected officials, military officers, and lawyers.

He played Jackie Cooper's stern but loving father in the drama Skippy (1931) and its sequel Sooky (1931).

Robertson also portrayed a flamboyant lawyer in Remember the Night (1940) and the straight sheriff in The Ox-Bow Incident (1943).

Robertson wrote the novel Moon Tide (1940), which was turned into Archie Mayo's drama thriller Moontide (1942)[4] starring Jean Gabin and Ida Lupino.