"(Sweden) highlighted its belief in equal rights regardless of sexual orientation as a fundamental principle of democracy," said Victoria Bell, a spokeswoman for the Swedish Foreign Ministry.
"The man, who is in his 50s, was sentenced February 4 to two years in prison for homosexual acts," she added.
Tunisia confirmed the conviction, but has not provided further comment.
A report in Swedish newspaper Aftonbladet said the man, who has been living in France for years, appealed the sentence.
Homosexuality is considered a crime in Tunisia, with convictions carrying a penalty of up to three years behind bars.
A Tunisian rights watchdog called on authorities to change the law and condemned the Swede's prison sentence.
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"This law is an infringement upon freedom," said Yamina Thabet, president of rights group ATSM. "The ATSM is repeating its call for the decriminalization of homosexuality."
Nearly three-quarters of African countries have laws against homosexuality.