"Prisoner Emad Ayyad has been freed, in exchange for two members of Al-Nusra Front who were being held by Hezbollah, after weeks of negotiations," the group's television channel reported.
Hezbollah confirmed the swap in a later statement without mentioning Al-Nusra.
It said Ayyad was exchanged for two "armed men", without specifying when he had been captured.
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A Hezbollah source, meanwhile, flatly denied any Al-Nusra involvement in the deal, referring instead to Ayyad's kidnappers as "gunmen in Qalamun", a Syrian region bordering Lebanon.
Hezbollah is allied to Syria's President Bashar al-Assad, and has sent thousands of fighters to support his army's bid to quell a nearly four-year revolt across the country.
The Lebanese group has played a key role in fighting around Damascus, especially in Qalamun.
The prisoner swap comes as Qatar-mediated talks try to secure freedom for 27 Lebanese soldiers held hostage by Al-Nusra and the Islamic State jihadist group since August after a fierce battle for the border town of Arsal.
Three soldiers held by Al-Nusra and IS have already been executed.