The Australian has become the first manager to pick up the award in his first two months working in the competition after he took charge of Spurs in the summer.
Postecoglou, who left Scottish champions Celtic to take the job in north London, has enjoyed a remarkable start and has led Tottenham to the top of the table.
Spurs remain unbeaten in the top-flight this season – winning six and drawing twice – with impressive victories over Manchester United and Liverpool.
That sees them sit above last season’s champions Manchester City as well as north London rivals Arsenal, considered by many to be the two biggest title favourites.
Tottenham’s glowing form comes despite losing Harry Kane to Bayern Munich in the summer transfer window, a move which most felt was going to hinder Spurs.
But Kane’s absence has been bringing the best out of the likes of Son Heung-min and summer signing James Maddison, who were named Premier League Player of the Month in September and August respectively.
Meanwhile, former Arsenal defender Bacary Sagna has dismissed Tottenham’s chances of winning the Premier League title despite their eye-catching start.
‘The title race will be between Arsenal and Manchester City, Spurs will collapse, as usual,’ Sagna told Paddy Power. ‘And that’s not just me speaking as an Arsenal fan. I don’t see them being consistent enough all season.’
Postecoglou, though, will take encouragement from the fact that the last manager to win the first two awards of any season was Jurgen Klopp in 2019-20, when Liverpool went on to lift the Premier League trophy.