Like Arnos Grove, Oakwood and Cockfosters, Southgate is a listed building in this case at Grade II* (regraded from Grade II in 2009) and retains much of its original decoration. The two escalators have the original column lighting, while bronze panelling is in evidence throughout the station. However; the station is not without change: in the late 1990s, one of the three entrances was filled in to be used as a new ticket office, and due to the design of the automatic barriers, one of the two remaining entrances is exit only.
In 2008 the station was extensively renovated, with new tiling at platform level, a partial new floor in the main ticket hall, and improved signage throughout. The station won the London Regional category award at the 2008 National Railway Heritage Awards for the modernisation of a heritage station