The controversial proposal by ITF president David Haggerty for an annual season-ending finals event from next year received a vote of 71.4 per cent at the federation's conference in Florida on Thursday, above the necessary two-thirds majority.
The makeover to one of sport's most famous and oldest global team tournaments has been a contentious issue within tennis but the ITF's plans received the necessary two-thirds majority from its 210 member nations.
The new format will involve a qualifying round in February, in which 24 teams will take part in home-and-away matches, with the 12 winners securing a direct place into the final.
- Barcelona football star Gerard Pique who leads the Kosmos investment group which is financing the new-look tournament. I feel very comfortable that this is not a risk for the Davis Cup.
The U.S. Tennis Association was among the national federations that backed the changes.
Aussie Davis Cup captain Lleyton Hewitt calls the plan a "money grab" and Davis Cup legend John Newcombe said it was "a recipe for the death of the Davis Cup as we know it".
Round-robin groups of three would send six group winners and two runners-up into knockout round playoffs.
Pique is among those who think the World Cup-style format is the boost the event needs.
"Today is a historic day and we are convinced that the agreement ratified by the nations certainly guarantees the future of the Davis Cup and the development of tennis at all levels", Pique said.
Another backer of the idea is USA billionaire Larry Ellison, who says he will invest in a revamped Davis Cup and says his Indian Wells facility is a candidate to host the event in 2021 after plans to host it for two years in Europe.
All matches, both singles and doubles, will be best-of-three sets rather than best-of-five.
Rafael Nadal is expected to play for Spain in the new Davis Cup competition next year.
Former Wimbledon champion Pat Cash described it in a tweet as "a sad day for men's tennis", accusing organizers of "fooling themselves" if they thought top players would be attracted to compete.
Regardless of this, the Davis Cup format's change is coming into effect, leaving Auger-Aliassime and other players like him, feeling left out in the cold by the ITF's decision.
"I am obviously totally against these changes to Davis Cup and pretty frustrated by what has occurred and the lack of information available", said Hewitt, a two-time victor of the Davis Cup and Australia's most successful singles player in the century-old event.
However, an increasing number of top players have opted not to play in recent years due to the hectic schedule.
Tennis Australia is one of several federations, including Germany and England, who voted against the plans. He also dearly wants to win the only ATP Masters 1000 title that has eluded him - nobody has won all nine.
The ATP intends to stage a revamped World Team Cup in Australia in the first week of January from 2020 - less than two months after the conclusion of the Davis Cup finale in November.
"This proposal takes away too much of what makes the Davis Cup special and unique", read a Tennis Australia statement.