The Greek-born Australian is the man who has finally been chosen to lead Celtic forward following a protracted 106-day hunt for Neil Lennon's replacement.
The Parkhead players are due to report back for pre-season training on June 17.
However, Postecoglou will not be there to greet them on their first day back - with the 55-year-old now preparing for a 10-day stint in quarantine on his arrival from Japan, where he has been coaching J-League outfit Yokohama F. Marinos.
But the former Brisbane Roar, Melbourne Victory and Australia national team boss insists he is already getting down to work as he sets about rebuilding a squad broken by last year's shattered 10-in-a-row attempt.
Postecoglou, who has signed a 12-month rolling contract, said: "The opportunity that has been given to me is one of the greatest honours in football and the responsibility to lead our magnificent football club into the future is one that I will cherish dearly.
"Celtic is one of 'the' names in world football, of that there is no doubt. A giant of a club, a proper footballing institution and so much more - real history, real substance, real authenticity and real soul.
"I know Celtic is a true way of life for so many people and I know the demands which come with this position - I am ready to do all I can to meet those demands.
"I will be doing everything I can to get our great club back on top and, at the same time, deliver the kind of football which our fans appreciate. We want to entertain our fans and we want to win, these are the objectives which I always set myself and which I now begin work on."
But Postecoglou faces a huge battle to win over the sceptical Hoops faithful, who are still reeling from the collapse of the club's move for first-choice target Eddie Howe.
Celtic have, however, convinced UEFA to hand their new manager an exemption on rules requiring bosses to possess a UEFA Pro-Licence - which Postecoglou does not hold - if they wish to manage in European competition.
European football's governing body has "endorsed" a similar qualification issued by Football Australia having also taken into account the former Socceroos boss' 25-year coaching career, which has seen him win league titles in his homeland and in Japan in between leading Australia at the 2014 World Cup in Brazil.
Postecoglou has now been given the green light to take his place in the dug-out when Celtic kick-off their Champions League qualifiers on July 20.
But he does not have time to waste, especially with a huge overhaul of last season's squad desperately required.
The worst-case scenarios will see the new man needing to sign as many as 15 new players, especially if the likes of Leicester-linked Odsonne Edouard and Newcastle target Kristoffer Ajer are allowed to leave.
But Postecoglou, whose only previous experience of managing in Europe was a nine-month spell in charge of Greek third-tier outfit Panachaiki, is backing himself to win over the supporters.
"When you think of Celtic, you think of supporters and my dream is to see our fans back at Celtic Park with us as soon as possible," he added. "We all hope things are changing for the better and can see our fans soon as they are vital to everything I want to do. We need our supporters back by our side and I can't wait to be with them back in a packed Paradise.
"I have already had great discussions with Peter (Lawwell), Dom (McKay) and the board about their ideas and strategy for the future of the club.
"I know the club's new modern vision aligns very much with mine and we now look to go and deliver on this. In everything we do we aim to give our fans a successful team of real quality, which they are excited about and can be proud of.
"We have already begun work on our plans for adding to the squad - we aim to bring players of quality to Celtic to enhance the existing core of great talent.
"I very much look forward to meeting with the players on their return from the close season break and I can't wait to get started as Celtic manager."