Majid Jamali Fashi, 24, who was sentenced to death in August last year, was said to have worked as an assassin for the Israeli intelligence service Mossad, receiving $120,000 for the hit, according to the BBC.
Fashi was hanged at Tehran's Evin Prison on Tuesday morning.
Majid Jamali Fashi, the Mossad spy and the person who assassinated Masoud Ali Mohammadi, our nation's nuclear scientist, was hanged on Tuesday morning, Iran's IRNA news agency reported.
The hanging comes as Iran gears up for crunch talks over its nuclear program in Baghdad next week, with world powers -- led by the U.S. -- pressing for access to its nuclear facilities, scientists and project documents.
Fashi was accused of murdering Ali Mohammadi, a 50-year-old Tehran University professor.
Mohammadi was killed outside his home in January 2010 after a remote-controlled bomb attached to a motorbike detonated.
Iranian scientists have been the subject of several fatal attacks over the last two years, with Iran accusing Israel and the U.S. of trying to sabotage what it says is a peaceful nuclear program.
The most recent attack occurred in January when Mostafa Ahmadi Roshan -- a chemistry professor and a director at the Natanz uranium enrichment facility near Isfahan in central Iran, and his driver, Reza Qashqei, died after two assailants attached a sticky bomb -- an explosive device with a powerful magnet on it -- to his car.
The type of attack used to kill Roshan was similar to that used in the killing of two other nuclear scientists, Majid Shahriari and Fereydoun Abbasi, in November 2010.
Iran declared that Israel, the CIA and Britain's MI6 spy agency were behind the attacks. The same was said after the attempted assassination of Abbasi, the head of Iran's Atomic Energy Organization.