Akram Afif rifled in a shot on the stroke of half-time to put the 2022 World Cup hosts ahead, before Almoez Ali doubled their lead after the break and Afif bagged a late third.
Over 80,000 fans initially packed into the Lusail Stadium, where Argentina beat France on penalties in the World Cup final 13 months ago. Qatar's win over Lebanon did not have the same drama and some spectators left as early as half-time.
By the final whistle there were swathes of empty seats. But it was a welcome start for a team that claimed their first Asian Cup five years ago and only changed their coach last month, with Tintin Marquez replacing Carlos Queiroz.
Qatar stunned Japan in the 2019 final in the UAE, lifting the trophy after winning every game. But they flopped on home soil at the World Cup, making a first-round exit.