MacNamara may be best known for his first printed novel, Valley of the Squinting Windows (1918). He continued to write for many years after the publication of this controversial novel. Later works include The Glorious Uncertainty (1923) and Look at the Heffernans (1926).
MacNamara married Helena Degidon, a schoolteacher, in 1920. He died at his home on Gilford Drive in Sandymount, County Dublin in February 1963.