The shot came after a flurry of heart-pumping moments with the Bulls first scoring six points in six seconds to take the lead.
But Lakers point guard Austin Reaves hit a clutch layup to put LA back on top.
It wasn't until Giddey launched a prayer at the buzzer that sent the fans inside the United Center into a frenzy.
The Bulls have now won four straight with two of those wins coming against the Lakers and the others against the Denver Nuggets and Sacramento Kings.
Standing with a 33-40 record, Chicago is currently sitting in ninth place in the Eastern Conference.