The body of the 51-year-old man was discovered outside Malaga airport on Friday morning.
An airport worker alerted police after finding the body bound to a bench.
Police said the man, who had been stripped from the waist down and had his hands tied behind his back, could have been sexually assaulted.
It is not immediately clear whether the man was waiting for a flight, had recently flown to Malaga or was in the area for another reason.
A Foreign Office spokesperson said: "We are in close contact with the Spanish authorities following the death of a man believed to be British in Malaga and are ready to provide assistance if needed."
Spanish police are examining CCTV footage around the airport.
Spanish police have launched an investigation after finding the body of a British man who had been tied up and may have been choked to death.