A police spokesperson said the operation launched early in the morning, went “smoothly” with “no major incident”.
The migrants have been transferred to police stations where a lengthy process of identification will follow.
Four unaccompanied minors who had been at the camps were to be sent to special hostels.
A growing number of migrants have been recently assembling in Patras, trying to smuggle themselves onto ferries to Italy.
The route from Patras, one of two ports linking Greece to Italy, is not new but when Europe’s refugee crisis began in 2015 and nearly a million people landed in Greece on boats, taking the overland route to countries like Germany was a safer option.
When those borders closed in March 2016 and a European Union deal with Turkey stranded over 50,000 refugees and migrants in Greece, Patras became the only option.