In 1970 Cannon appeared as Roy Harkness on The Men from Shiloh, the retitled name for the final season of TV western The Virginian in the episode titled "Hannah".

He played a recurring character – a lawman named Harry Briscoe working for the Bannerman Detective Agency - in the 1971 to 1973 series Alias Smith and Jones.

His film credits included An American Dream (1966), Cool Hand Luke (1967), Krakatoa, East of Java (1969), The Thousand Plane Raid (1969), Heaven with a Gun (1969), Cotton Comes to Harlem (1970), Lawman (1971), Scorpio (1973), Raise the Titanic (1980), Death Wish II (1982) and Beyond Witch Mountain (1982).

Cannon was a founding member of Joseph Papp's New York Shakespeare Festival, starring in their productions of The Taming of the Shrew (1956) and Much Ado About Nothing (1961).

[4] Cannon married Alice McCamley, an actress and writer who appeared in Broadway productions including Company and Johnny Johnson.