Mullin is originally from Frenchbrook, Kilmaine, County Mayo. He studied corporate law at NUI Galway. During his free time he worked with MidWest Radio and The Connaught Telegraph. A career change of mind prompted him to take the Higher Diploma in Applied Communications at NUIG around 2001. He then worked as a Sports Sub-editor with the Evening Echo before working for a year as a sports reporter with The Mayo News, sports editor of fledgling publication The Athlone Voice from September 2003 until 2006, then deputy sports editor with the fledgling Irish Daily Mail before applying for the RTÉ job. Mullin began working for the RTÉ News Sports Unit in October 2006.
