The building, which serves a mosque for Svenljunga's Muslim Association was vandalised, with the text ‘Viva La France’ sprayed on an outside wall, in reference to the terror attack on satirical magazine Charlie Hebdo in Paris last week.
A pork's head was also left outside the premises.
According to the Koran, Muslims are not supposed to eat pork.The discovery was made by worshipers on Sunday and became known to Swedish media on Monday.
Police in the region are investigating.
Local media in Borås say it is not the first time that vandalism of this kind has taken place in the area. In October 2013 a pig’s head was left outside a mosques in a nearby town, Limmared.
The news follows several other attacks on mosques in Sweden in recent weeks, amid fears of rising Islamophobia in the country.
Last week, Mohammed Fazlhashemi, Professor of Islamic theology and philosophy at Sweden's Uppsala University told The Local on Thursday that he feared "counter attacks" following the Paris shootings were likely and said that many Muslims in Sweden now feared for their safety: "We've seen Islamophobic rhetoric gradually strengthening in Swedish society…we may see reprisals in Sweden".