Following a glitzy opening ceremony with Qatar's ruler Sheikh Tamim bin Hamad al-Thani also in attendance at the Lusail Stadium, the two forwards stole the show to kick off the tournament with three points in the bag for the hosts.
Qatar had an early goal ruled out for offside but after a period of dominance, Afif finally broke the deadlock on the stroke of halftime when he pounced on a lay-off by Ali in the box to make it 1-0.
Ali, top scorer in the 2019 edition, then doubled the lead in the 56th minute when he headed home Mohammed Waad's inviting cross from the left flank.
Lebanon had their moments on the counter-attack to give their travelling fans some hope, but Qatar held firm to deny their Middle Eastern counterparts.
Afif sealed the victory in stoppage time when he pounced on a botched clearance and easily accelerated past a tiring Lebanon defence before applying a calm finish to make it 3-0.
"Akram was named the most valuable player of the match, he's a very high-quality player and he deserves that," Qatar coach Marquez Lopez told reporters.
"I was very happy with the match and how we delivered on our own pitch, the players gave 200% of what was required."
