Rathmullan House was built around 1820 as a summer residence for the family of Lieutenant Colonel Andrew Knox, whose main home was the splendid Prehen House in Derry

The Knox family connection with Rathmullan goes back to Bishop Andrew Knox  in the early 1600s.

The house and estate was sold in 1837 to Thomas Batt, a member of a prominent Belfast family, founders of the Belfast Bank.
The Batts remained in Rathmullan for around a century.  Just before the Second World War, the house was sold again, this time to the Holiday Fellowship, a Christian group which organised walking holidays. It was also used by the Irish army reserve during the war years.