The Blackhawks won their fourth in row and have managed at least one point in 17 of their 19 games this year.
Chicago let an early two-goal lead get away and found itself trailing heading into the third period. Pirri, however, deadlocked the game just three minutes into the stanza with a deflection.
He scored again in the fourth round of the shootout to end the Coyotes' brief winning streak at two games.
Michael Stone had two goals for Phoenix.
Pistorius testifies he didn't consciously pull trigger when he shot girlfriend
Pot vending machine to debut