The June 12 vote triggered big street demonstrations by opposition supporters accusing the authorities of rigging the result, which gave President Mahmoud Ahmadinejad a second term in charge.
Abdullah Momeni's wife told website Mowjcamp, which backs defeated candidate Mirhossein Mousavi, that Momeni was sentenced to six years for taking part in post-election protests and two years for previous activities concerning national security.
Several other post-election detainees have received jail terms and three people have been sentenced to death, according to Iranian media.
Last week a court sentenced a man to seven years in jail and 74 lashes for post-election activities, Mowjcamp reported.
Thousands of people were detained after the election five months ago. Most of them have since been freed, but more than 100 have been charged with fomenting post-election street unrest, including senior reformist figures.
The authorities deny opposition charges that the poll was rigged to secure President Mahmoud Ahmadinejad's re-election and accuse foreign powers of stoking the unrest that erupted in the days after the vote.
Ahmadinejad has championed Iran's nuclear energy programme, which has led the country into confrontation with Washington and Western powers and brought U.N. sanctions. (Reporting by Hashem Kalantari; writing by Andrew Hammond; Editing by Charles Dick)
