Hannibal Gadhafi appeared in a video aired late yesterday on local Al-Jadeed TV saying anyone who has information about Imam Moussa al-Sadr should come forward.
Gadhafi appeared to have been beaten up and had black eyes but said in the video he is "in good health, happy and relaxed."
It was not clear when Gadhafi, who is married to a Lebanese woman, was kidnapped.
Al-Sadr, one of Lebanon's most prominent Shiite clerics in the 20th century, vanished, along with two other people, during a trip to Tripoli in 1978.