Since 1991, Argentina has had two championships each season, and the current top division has 20 clubs.
Relegation will be determined in the same way, by using a team’s average points over three seasons, but under the new format only two will go down instead of the current three.
“The new tournament will be calmer and more even in sporting terms,” Grondona told local Radio 10 on Wednesday.
“All the directors (on the AFA committee) raised their hands to approve the change,” added the 82-year-old, who has for some time wanted to include more teams from the provinces in a top flight generally dominated by the Buenos Aires clubs.
Grondona took the top job at the AFA in 1979 and will retire in 2015.
The AFA said in a statement the new championship “will played on a league basis with teams playing each other once in 29 rounds with a 30th round for a repeat of the ‘clasicos’ (derbies)”.
Grondona’s decision to enlarge the top flight means 10 teams will emerge from a shortened 22-team second tier championship in the second half of this year, while the first division will play one last tournament of 20 teams.
The AFA introduced the two-championships format in 1991 while also aligning Argentina, whose traditional season went from February to November, with Europe, with the first competition running from August to December and the second from February to June.
The names changed last season from Apertura to Inicial and Clausura to Final though the format remained the same as Grondona continued to tinker with a system that will be his legacy after his reign ends.
The new top division will run from February to November next year. The AFA did not specify if there would be a mid-season break.
The three teams to be relegated at the end of the current campaign could now return to the top flight at the end of this year under the new format.
The earliest they could return under the current system would have been June 2015.
Argentinos Juniors, who discovered Diego Maradona, Juan Roman Riquelme and Esteban Cambiasso, won their third league title in 2010 but were relegated last weekend after several years of mismanagement.
The two other relegation spots will be decided over the remaining three matches of the Final championship.
(Editing by Peter Rutherford)