He played Gaelic football with his local club Fermoy and was a member of the Cork senior inter-county team from 1944 until 1947.
Magnier first came to Gaelic football prominence as a 17-year-old member of the Fermoy team that claimed the County Intermediate Championship title in 1932.
Magnier collected a Munster Championship in his first year with the team, however, it would be 1945 before he joined the starting fifteen.
He won his second provincial medal that year before ending the season by lining out at right corner-back when Cork claimed the All-Ireland title after a defeat of Cavan in the final.
Magnier died after a period of ill health at the Regional Hospital in Cork on 10 July 1979.