Killarney is small, with a full-time population of about 7,000. The town is built around one central thoroughfare, Main Street, which changes its name to High Street at midpoint. The principal offshoots of Main Street are Plunkett Street, which becomes College Street, and New Street. The Deenagh River edges the western side of town and East Avenue Road edges the eastern side.

The busiest section of town is at the southern tip of Main Street, where it meets East Avenue Road. Here the road curves and heads southward out to the Muckross road and the entrance to Killarney National Park.