"For the first time it will actually be Christmas when it actually is Christmas (instead of February)," said Channel 5's Greg Barnett.
He added that is would also "reduce online spoilers and piracy".
The current time lag between the UK and Australia is two weeks; to close the gap Channel 5 will air 10 episodes between December 7 and 18.
Neighbours, Australia's longest-running drama, is currently shown twice a day at 13:45 and at 17:30. The simultaneous broadcast will begin on 4 January 2016.
"At a time when online piracy can often mean hardcore fans' enjoyment of continuing drama is spoilt, this is great news for our millions of Neighbours fans," said Barnett.
He promised "the new year [would] start with a bang for Ramsay Street rotter Paul Robinson". Robinson, played by actor Stefan Dennis, has been with the show since its inception in 1985.
Originally broadcast on BBC One, the Melbourne-based soap - which celebrated its 30th anniversary this year - moved to Channel 5 in 2008.
The show, which at its peak drew a combined UK audience of 19 million every day, has been responsible for launching the careers of Kylie Minogue, Guy Pearce, Natalie Imbruglia and Margot Robbie. It now reaches around 1.5 millions viewers daily.
Channel 5 also broadcasts fellow Australian soap Home and Away. The show currently runs eight weeks behind Home and Away's Australian broadcasts.
From January, Channel 5 is to begin broadcasting episodes of Neighbours on the same day as they air in Australia.