Local Organising Committee CEO Danny Jordaan told reporters the LOC board of directors had decided to raise the allocation from 11 percent to give poorer South Africans more chance of seeing games.
The decision should help sell tickets amid sluggish sales to foreigners but may also knock expected revenue from the month-long tournament, starting in South Africa on June 11.
Jordaan said the decision followed appeals from fans, trade unions and politicians to accommodate poor South Africans, but stressed that the loss of income would not harm the running of the tournament.
"We have made this commitment that we want the tournament to be affordable, that those football fans who have been supporting football for all of these years must now not be excluded," he said.
"Therefore we should then move the percentage of tickets available in category 4 to 29 percent and therefore accommodate all of those who made the ticketing request in category 4."
Category 4 tickets are specially-priced for South African residents at 140 rand ($17.95) for group matches, a quarter of the price of the cheapest tickets in other categories. They are still more than six times the cost of seats for local premier league matches.
Critics have long argued that the price of tickets were too expensive for most football fans in South Africa, where tens of millions of people live in poverty.
"At the beginning we argued ... that you have to take into account that football fans in South Africa are working class people of low income, and therefore we created a special category 4 ticket," Jordaan said.
"What we saw from the ticket requests from South Africans is much more than 11 percent."
So far 2.24 million tickets have been sold, leaving 660,000 still available just over 100 days before the start of the World Cup.
Organisers had originally estimated the tournament would attract about 450,000 foreign fans.
FIFA general secretary Jerome Valcke told reporters earlier this week that organisers would not cut ticket prices to ensure capacity stadiums, although FIFA could look to increase the category 4 tickets to 20 percent.
