It is within the townland of Ballyrobert,[1] with Holywood to the west and Helen's Bay and Crawfordsburn to the east.

Seahill was once a stand-alone settlement but it is now joined to Holywood and the Greater Belfast conurbation.

Seahill is classified as a village by the NI Statistics and Research Agency (NISRA) (i.e. with population between 1,000 and 2,250 people).

On Census day (27 March 2011) there were 1,018 people living in Seahill.

Of these: Seahill railway station was opened on 4 April 1966.