Mellett first came to sporting prominence as a schoolboy with Trim CBS.[citation needed] At club level, he lined out with Martinstown and won a Meath JFC in 1969 and a Meath IFC as part of a Martinstown-Athboy selection in 1979. Mellett first appeared on the inter-county scene as a dual player at minor level in 1963. He was selected for the Meath junior football team in 1966, while also lining out in both codes in the under-21 grade. Mellett was promoted to the senior team for a challenge game against Leitrim and was a member of the extended panel for the 1966 All-Ireland final defeat by Galway. He made the starting fifteen the following year and was at left wing-forward for the defeat of Cork in the 1967 All-Ireland final.[2] Mellett's other honours include three Leinster Championship medals.[citation needed]