Global press freedom groups condemned the convictions after a trial which had fueled concerns of international donors over the West African country of 1.8 million, a tourist destination for European holidaymakers.
The journalists include three members of the Gambian Press Union, two reporters from The Point newspaper and one working for Foroyaa newspaper. One of the journalists for The Point, Pap Saine, also reports for Reuters.
The court in the capital Bajul sentenced them to two years in prison and fines of 250,000 dalasi (USD 9,700) each, said the source, who was present at the hearing.
Seven were arrested in June after the Gambia Press Union issued a statement critical of the government's treatment of journalists, especially after the killing in 2004 of veteran reporter Deyda Hydara. One of the seven was later released.
The verdict was condemned by the New York-based Committee to Protect Journalists, which described it as another blow for the independent press in Gambia.
"It was a highly politicized trial," said Tom Rhodes, Africa Program Coordinator.