It is bounded on the north & west by Knockateggal townland, on the east by Ummera & Gortineddan townlands and on the south by the international border with County Cavan and the Republic of Ireland. Its chief geographical feature is Slieve Rushen mountain on whose eastern slope it lies reaching to an altitude of 270 metres above sea-level. The townland is traversed by the B127 Border Road to Ballyconnell and some minor lanes. Gortmullan covers an area of 315 statute acres.