He represented Dundas in the House of Commons of Canada from 1917 to 1921 as a Unionist member.

He was born in Chesterville, Canada West, the son of James C. Casselman, and was educated in Morrisburg and Hamilton.

He taught school for two years before opening a general store in Chesterville.

Casselman was a recruiting officer and served overseas during World War I.

His half-brother William H. Casselman served in the Ontario provincial assembly.