Although La La Land had been announced by Warren Beaty as the winner, the wrong information had been included in the envelope and Moonlight was the actual Oscar winner for Best Picture.
With crowd on its feet and suddenly in shock, the La La Land cast left the stage in disbelief, as the Moonlight cast uncertainly made its way to the podium.
Beatty, 79, took the microphone and explained to the crowd with an awkward grin that the announcement card had read “Emma Stone, Lala Land”, which he found odd at the time.
So the question on everyone's lips was, 'Who is to blame?'.
Was it Warren Beatty? Was it Faye Dunaway? Or was it La La Land producer Jordan Horowitz?
But it turns out the London-based accounting and "professional services" firm, PricewaterhouseCoopers, that has managed the Academy Awards winners for years, has taken the fall for the mix-up.
"We sincerely apologise to “Moonlight,” “La La Land,” Warren Beatty, Faye Dunaway, and Oscar® viewers for the error that was made during the award announcement for Best Picture," the company said in a statement to Mashable.
"The presenters had mistakenly been given the wrong category envelope and when discovered, was immediately corrected. We are currently investigating how this could have happened, and deeply regret that this occurred. We appreciate the grace with which the nominees, the Academy, ABC, and Jimmy Kimmel handled the situation.