The parish of Tjømø was established as a municipality January 1, 1838 (see formannskapsdistrikt).
It is wholly located on islands, the main island being the Tjøme island, where "Tjøme sentrum" is located, along with the shops, schools and restaurants. There are a few other central areas on the islands such as Hvasser, with active fishermen as well as the tourist industry for the bypassing travellers, with an icebar, shops, boat petrol station and a number of places to buy food and supplies.
There are approximately 4,600 permanent residents on the island, but in the Summer months this number rises to around 40,000 inhabitants, including the Norwegian Royal Family who have a summer house on the island. The reason for the extreme increase is mainly the sea sports available in the area and the remarkably good weather. Summers on Tjøme are both warm and sunny, and the beaches are filled with locals and tourists. Tjøme has been nicknamed "Sommerøya" which means 'the summer island'. Tourists mostly from "the Oslo area" visit this charming island.
Verdens Ende, in English known as the 'World's End', lies at the southern tip of Tjøme Island, and has for years been visited by tourists. Ironically enough, it is not really the end of the world in any sense, but when one stands there and looks out across the vast area of ocean one can forget about the geography and really feel like there is nothing else out there.
Tjøme is also a great place for hikes, even though they are limited by the size of the island. The spectacular seaside scenery can be seen all year round.
Until 1918 the name was written "Tjømø".