Mackay had been set to meet Tan on Saturday but instead, Cardiff issued an abrupt statement early on Friday afternoon confirming his departure, leaving coaches David Kerslake and Joe McBride to take charge for Saturday's clash with Sunderland.
The statement read: "The Board of Directors at Cardiff City Football Club have today relieved Malky Mackay of his duties. A new first-team manager will be appointed and announced in due course."
Tan subsequently released a personal statement, adding: "There has been a good deal of publicity generated by and about Mr Malky Mackay over the last few months.
"Indeed far too much dirty linen has been exposed to the public gaze. But, I stress, not by me. Indeed, I have deliberately not responded to this, hoping that the Club can be judged on its football rather than personalised arguments about who said what to whom.
"I have, however, regretfully concluded that it is no longer fair to the Club, its players, its fans, or the public more generally, for this uncomfortable state of affairs to continue. Cardiff City Football Club means far too much to us all for it to be distracted by this."
Mackay was appointed Cardiff boss in June 2011 and having guided the team to the Championship title last year, leaves after 125 games in charge with a win rate of 43%.
The 41-year-old insists he leaves the Welsh capital with his head held high having taken the team to Wembley for the League Cup Final and play-off decider as well as taking Cardiff to the top flight for the first time since 1962.
"It is with the deepest and most sincere regret that I today confirm my sacking as manager of Cardiff City FC," Mackay said.
"As disappointing as today's decision is, I am already able to look back at my time at Cardiff City FC with immense pride and joy given the number of milestones the club achieved during the last two-and-half years.
"I would like to thank my players, all of my direct footballing staff, all the people behind the scenes at the club and most importantly the people of Cardiff, who have stood behind me resolutely throughout my time here and especially in these recent turbulent months.
"I leave with my head held high having gained a level of experience that, upon reflection, I suspect would have been difficult to find anywhere else in British Football."
Early reports suggest that former Manchester United striker Ole Gunnar Solskjaer, in charge of Norwegian club Molde, will be among those targeted by club chairman Mehmet Dalman with a view to taking the reins, with Cardiff currently just one point above the Premier League relegation zone.
There was a significant reaction in Turkey, where the agent of experienced coach Yilmaz Vural appeared confident his man was in the running to land control of the Welsh club.
Muzzi Ozcan said previously via Twitter: "The story is coming to a [sic] End in Wales and a new story will be born ... The next 48 hours will be explosive!"
When news of Mackay's sacking broke, he added: "New page has been turned over as I said .... Wish the best for MM."
Malaysian owner Tan has courted controversy several times since purchasing a controlling share in the club back in 2010.
Large sections of City fans took exception to his decision to change the club's colours from blue to red, and he then fired Mackay's head of recruitment Iain Moody without consulting the Scot.
Last week, Tan issued an ultimatum to Mackay insisting that if he failed to tender his resignation, he would be sacked - prompting around 200 Cardiff supporters to launch a protest ahead of the 3-0 Boxing Day defeat to Southampton at the Cardiff City Stadium.