The poll, commissioned by Aamulehti from the pollster Taloustutkimus, showed that 58 percent of those surveyed are in favour of changing the law to allow people of the same gender to marry.
The greatest backing was found among people under 35 years of age, three-quarters of whom would like the law changed. The most opposition was expressed among those over 65, more than half of whom would prefer the law to remain as is.
Just over half all respondents, 51 percent, would also give full adoption rights to same-sex couples.
The survey was answered by 1,002 people between March 4 and 7. The margin of error for the results is 3 percentage points.