The number has fallen to an all-time low just four months before kick-off, a survey has found.
Many of those polled have criticised the tournament as a waste of money that would be better spent elsewhere, a poll showed on Monday.
The survey by local pollster Datafolha showed that only 52% of Brazilians favored hosting the event, down from a high of 79% in November 2008, a year after Brazil was chosen as the venue for the 32-nation event.
Support for the event has waned since massive protests broke out in June against poor public services and the high cost of building stadiums for the World Cup.
But the Datafolha poll also showed the demonstrations, which have become smaller and more violent as masked anarchist groups clash with police, were losing support.
The survey showed 38% of Brazilians were against hosting the event, up from 10% in 2008.
Last week, another poll found 80% of Brazilians would not want the World Cup to be held in their country if the decision was made today.
Brazil has won five World Cup titles - more than any other nation.