The fishermen from Jagadapattinam in Pudukottai District were detained off Karainagar in northern Sri Lanka, a state Fisheries official said.
They were later taken to Kangesanthurai port, Fisheries Assistant Director Sivakumar said.
This is the second instance of arrest of Tamil Nadu fishermen by the Lankan Navy this month. Earlier, on July 6, eight fishermen, also hailing from Pudukottai district, were taken into custody and their two boats seized.
There has been a spurt in the detention of Indian fishermen by Sri Lanka since last month, when more than 50 fishermen were held, prompting state Chief Minister Edappadi Palaniswami to seek the intervention of Prime Minister Narendra Modi to secure their release.