Sky News' Alex Crawford and Garwen McLuckie were detained by police after she spoke with Pastor Evan Mawarire near the capital Harare.
She was in the country to report on the clergyman's 'stay at home' protests to try and shut down the Zimbabwe economy, forcing the president to step down.
Pastor Mawarire, 39, had called for mass walk outs of workers using the hashtag #thisflag on Twitter.
In recent months Zimbabwe's civil servants have not been paid and the economic crisis in the country has deepened.
Robert Mugabe, 92, has led the country since independence in 1980 with many arguing he has brought the country to its knees.
Ms Crawford and her colleague were travelling on British passports but police say they did not have the required documentation to report in the country.
But she was invited by officials, she said: "We were held in a room for about 12 hours while we were questioned by a large group of officials, our bags searched, telephones examined and all personal and official documents inspected with some removed and photographed.
"We asked to see a lawyer but were refused access to him when he arrived at the airport. He was asked to remove himself from the airport grounds."
The pair were deported and authorities warned a similar fate would meet other journalists trying to work in the country without state control.
