The carrier will offer a four-per-week service from Terminal 5 to the Moroccan city from October 28 with flights departing on Thursday, Friday, Saturday and Sunday.
BA already flies from Gatwick to Marrakech eight times a week.
Return fares lead in from £132pp in Euro Traveller and £332pp in Club Europe.
Sean Doyle, director of network and alliances, said: “Marrakech adds another exciting destination to our leisure network at Heathrow and is a fantastic starting point to explore Morocco; from trekking in the Atlas Mountains to discovering the amazing deserts and beaches and soaking up the atmosphere of the many medinas.
“Marrakech is one of the key tourism destinations in North Africa, so we’re excited to serve it from two of our London airports.”
