According to the poll, which surveyed 1,000 people, 17% said they did not know.
Aalto University professor of energy technology Sanna Syri said the figures reflect “practical” Finnish attitudes towards nuclear-produced electricity.
“One factor that explains this is probably that the utilisation of Finnish nuclear power plants is among the best in the world,” Mr Syri said.
Positive attitudes towards nuclear power are higher among 15-24-year-olds, according to the poll. Nuclear power was considered sustainable by 52% of this demographic, while 29% said it was not sustainable.
Finland has four commercially operational nuclear plants providing about 32% of its electricity. It also has a new unit under construction at Hanhikivi.