It was two goals from the more established Italian Ciro Immobile which helped Lazio maintain their unbeaten start to the season as they edged Genoa 3-2.
Bastos gave the side from the capital the lead after 13 minutes but Pellegri had the home team level 12 minutes after the break.
Immobile grabbed his first of the game in the 70th minute but the advantage lasted just three minutes, with Pellegri grabbing his second before Immobile scored the winner with eight minutes remaining.
The Italy striker now has nine goals in six games in all competitions for I Biancocelesti this season as they sit fourth in the table.
But it is Pellegri who will grab the headlines, having added his first goals since becoming the youngest scorer in the history of Italy’s top-flight earlier this year.
He found the net in the 3-2 loss by Roma in May, becoming the first player born in 2001 to score in Serie A.