Somero has been known as a trading place since the 14th century. The municipality was officially founded in 1867. The municipality of Somerniemi merged with Somero proper in 1977. Somero was moved from the province of Häme to the province of Turku and Pori in 1990. Currently it belongs to the province of Western Finland. Somero became a town (kaupunki) on January 1, 1993.

Häntälä Hollows are the traditional biotope area in the villages of Häntälä, Talvisilla, Syväoja and Kerkola. The nature trail that begins at the Häntälä Village House is located in the area, where it is possible to explore its traditional landscapes. Häntälä Hollows is part of the wider Natura 2000 area of the Rekijokilaakso, which also extends to the city of Salo. The most significant main roads in Somero are the national road 52 through the town center and the regional road 280 in south of the town center, which is the most direct road connection to Helsinki.