Sri Lankan police said Naomi Michelle Coleman, 37, was arrested at Bandaranaike International Airport in the capital, Colombo, after she arrived from India.
A police spokesman said she was arrested for "hurting others' religious feelings" after the tattoo of a Buddha seated on a lotus flower was spotted on her right arm.
Buddhism is the religion of the country's majority ethnic Sinhalese and Buddhist tattoos are seen as culturally insensitive.
Coleman later appeared before a magistrate who ordered her deportation.
The spokesman said she was being held at an immigration detention centre until deportation and would be removed "very soon".
Another Briton, Antony Ratcliffe, was reportedly deported for showing a Buddha tattoo on his arm in March last year.
A Foreign and Commonwealth Office spokeswoman confirmed the detention of a British national in Sri Lanka on Monday, and said they were providing assistance.