Mr Nabavi is a former minister for industry in the Iranian government
An Iranian appeals court has upheld the sentence of a senior reformist figure convicted for his role in unrest after elections last year.
Former industry minister Behzad Nabavi was given a five-year sentence by the court, the semi-official Iranian Students News Agency reported.
Another unidentified man was given a death sentence for protests during December 2009.
Mr Nabavi is the second opposition leader jailed this week.
Eight other protesters were also sentenced to various prison terms on Tuesday, the news agency reported.
On Monday, opposition leader Mohsen Aminzadeh was convicted of organising protests, disturbing security and spreading propaganda against the system, his lawyer said.
RECENT UNREST IN IRAN
19 Dec: Influential dissident cleric Grand Ayatollah Hoseyn Ali Montazeri dies aged 87
21 Dec: Tens of thousands attend his funeral in Qom; reports of clashes between opposition supporters and security forces
22 Dec: Further confrontations reported in Qom
23 Dec: More clashes reported in city of Isfahan as memorial is held
24 Dec: Iran reportedly bans further memorial services for Montazeri except in his birthplace and Qom
26 Dec: Clashes reported in central and northern Tehran
27 Dec: At least eight dead following anti-government protests in Tehran; 300 reported arrested
Last month Iran hanged two activists it said were guilty of "war against god", a charge levelled at those who protested against the disputed election of Mahmoud Ahmadinejad in June.
Aminzadeh was a prominent supporter of the defeated presidential candidate Mir Hossein Mousavi.
Correspondents say the authorities are tense ahead of the 31st anniversary of the Islamic Revolution on Thursday.
Opposition supporters have called for widespread anti-government protests to coincide with official rallies. The police have meanwhile warned that opposition demonstrations will be firmly confronted.
In December, eight people were killed in clashes at demonstrations on Ashura, one of the holiest days in the Shia Muslim calendar.
Mr Mousavi's Green Movement said last June's poll had been rigged to ensure the re-election of President Mahmoud Ahmadinejad, a charge the government denied.
At least 30 protesters have been killed in clashes since the election, although the opposition says more than 70 have died.
More than 80 people have been jailed for up to 15 years - including former government spokesman Abdullah Ramezanzadeh, former vice-president Mohammad Ali Abtahi and former deputy economy minister Mohsen Safaie Farahani. Some 200 activists remain in detention.