Uefa president Aleksander Ceferin said it meant "the dream to participate will remain for all clubs".
A previous proposal to award two Champions League places to clubs on the basis of their historic performance in European competition will not come into effect.
Under that rejected proposal, those places would have been assigned on the basis of a club's coefficient.
Uefa has clearly shown today that we are fully committed to respecting the fundamental values of sport and to defending the key principle of open competitions, with qualification based on sporting merit, fully in line with the values and solidarity-based European sports model," said Ceferin.
We are convinced that the format chosen strikes the right balance and that it will improve the competitive balance and generate solid revenues that can be distributed to clubs, leagues and into grassroots football across our continent while increasing the appeal and popularity of our club competitions.
Ceferin said the new format had been approved unanimously by Uefa's executive committee, with the agreement of Europe's league bodies and national associations.
He added: "Qualification will thus remain purely based on sporting performance and the dream to participate will remain for all clubs.
Under the new format, each team will play eight games over 10 match weeks.
Two of the additional four places will be awarded on the basis of the highest performing countries in each individual season of Uefa club competition.