Nadal invited people affected by the severe storms to take shelter at his tennis academy in nearby Manacor and then donned boots to join other volunteers in clearing away mud and water from affected areas.
The Foreign Office said in a statement: "We are in contact with the Spanish authorities responding to flooding in Majorca, and urgently seeking updates from them".
Susan Guile and John Gray jetted out to the Balearic Islands on Sunday (7) for an 11-night holiday.
The Foreign Office said it was "urgently seeking updates" from their Spanish counterparts about the fate of any British people stranded in the area.
Two of those killed were in Sant Llorenc, one in Arta and two more in S'Illot.
Officials have said more than 600 rescuers and medical staff were at work and that emergency relief centres had been set up in sports halls.
"My honest condolences to the relatives of the deceased and injured by the severe floods in San Llorenc".
Image Heavy rain and flash floods hit Sant Llorenc de Cardassar on the island of Mallorca Spain
Videos shot on mobile phones by local residents showed a strong current of water and mud that buried cars and tore trees on its way down the streets of the town of 8,000.
Cars piled up after the flood..
Hundreds of displaced people are now being forced to shelter in emergency accommodation.
Prime Minister Pedro Sanchez called news of the flooding "devastating " on Twitter: "My solidarity and support goes out to the families and friends of victims and all the affected by these tragic floods".
"It all happened in less than 10 minutes", a witness told Spanish TV.
Some parts of the island received up to 9in (23cm) of rainfall in around four hours on Tuesday evening.
The weather agency, AEMET, said more heavy rainfall is expected Wednesday in eastern and southern parts of the Iberian peninsula.