Leonardo Shahin converted his penalty in the 56th minute to seal a 1-0 win for the Lebanese side.
Iran put Lebanon under pressure and created so many chances but their strikers failed to capitalize on their chances.
Iran failed to win a match and score a goal in the tournament. The young Persians started the campaign with a goalless draw against Korea Republic and also played out a goalless draw against Uzbekistan.
Uzbekistan defeated Korea Republic 2-0 in another Group C match.
Uzbekistan and Korea Republic advanced to the knockout stage with seven and four points, respectively. Lebanon came third with three points and Iran sit the bottom of the table with just two points.