The Northern Irishman secured the windfall after beating closest challenger Xander Schauffele by four shots
Rory Mcllroy is set to earn a staggering €15million (£12.3million) after winning the Tour Championship and FedEx Cup title for the second time in four years in Atlanta.
McIlroy carded a closing 66 at East Lake to finish 18 under par, four shots ahead of American Xander Schauffele.
World number one Brooks Koepka, who held a one-shot lead after the completion of the delayed third round, ran up a double bogey on the seventh and carded a hat-trick of bogeys on the back nine to drop back into a tie for third with Justin Thomas.
McIlroy began the week by questioning both the radical new format and the focus on the extraordinary prize money on offer, but ended it with a third win of the season following victories in the Players Championship and Canadian Open.
Starting this year, the player who had the most FedEx Cup points after the BMW Championship started the first round of the Tour Championship on 10 under par, in this case Thomas.
The second-highest points earner began at eight under, the third-ranked player at seven under and so on, on a sliding scale down to the players in 26th to 30th who started on level par.
McIlroy started on five under par and had reached 14 under by the end of the third round, which had been suspended on Saturday afternoon due to bad weather around 30 minutes before lightning strikes resulted in five spectators being taken to hospital.
The Northern Irishman and Koepka both started the final round with five straight pars before making a birdie on the par-five sixth, but the turning point came at the next as Koepka made a double bogey following a lost ball off the tee and McIlroy holed from 20 feet for birdie.
Koepka responded superbly to birdie the next as McIlroy enjoyed a major stroke of luck when his pulled approach hit a tuft of grass on the edge of a drain and stopped short of the water.
Birdies on the 12th and 13th took McIlroy four shots clear and although he bogeyed the next two holes and had to hole from eight feet on 16 to avoid an unwanted hat-trick, McIlroy effectively sealed victory with a birdie on the 17th and rounded off the week in style with another on the par-five 18th.