The tournament of continental champions is a key staging post in Brazil's preparations to host next year's World Cup and the five-time world champions made the opening game one to remember.
Neymar, the 21-year-old superstar who will play for European superpower Barcelona next season, started the party in only the third minute with a crisp half-volley from 20 yards that fizzed into the top-right corner.
Second-half goals from Paulinho and substitute Jo completed a morale-boosting victory for the Selecao, who had won just two of the first seven games since the return of 2002 World Cup-winning coach Luiz Felipe Scolari.
"If we continue to play in this manner, we could become a team capable of beating anyone," said Scolari, popularly known as 'Felipao' (Big Felipe).
The afternoon at the newly renovated Estadio Nacional had begun with a flamboyant opening ceremony that celebrated Brazilian culture and featured some 2,600 exuberantly dressed volunteers.
Designed by artistic director Paulo Barros, a two-time award-winner at the Rio de Janeiro carnival, the 20-minute show drew cheers from the yellow-clad hordes in the arena, which hours before had witnessed tense scenes.
Protests outside the venue yielded 20 arrests and left two dozen people injured, after riot police had to deploy a roadblock to prevent a swarm of demonstrators reaching the stadium in the Brazilian capital.
Angry at the allocation of funds towards the organisation of sporting events at a time of acute social inequality, young protestors chanted: "I renounce the Cup! I want more money in health and education!"
Police colonel Adilson Antonio Evangelista told AFP 20 people were arrested, while seven policemen and 23 demonstrators were hurt after police forced the crowd back with tear gas and plastic bullets.
The march followed a demonstration by homeless activists in the same spot on Friday; and police made hundreds of arrests on Thursday when protests against rising mass-transit prices in Rio, Sao Paulo and Porto Alegre became violent.
Students also protested peacefully in Belo Horizonte on Saturday, and there are plans for another demonstration against public transport price hikes in Rio on Sunday.
In all, Brazil is set to shell out some $15 billion (11 billion euros) through to the World Cup in 2014.
Rio then will host the 2016 summer Olympics, and the city has seen real estate and rental prices soar to exorbitant levels, with some observers predicting a corrective crash after the sporting caravan has moved on.
The Brazilian government drafted in 3,700 troops to bolster security in the capital for Saturday's match, with as many military police also on hand in a billion-dollar operation covering the six venues as a whole.
FIFA president Sepp Blatter and Brazil President Dilma Rousseff were met with jeers as they declared the tournament open prior to kick-off between Brazil and Japan.
"We are all united for a true fiesta of football in the land of the five-time world champions," said Blatter.
In a further headache for organisers, the tournament began with only seven of the eight competing teams present: Nigeria's arrival was delayed until the early hours of Sunday morning due to a dispute over bonus payments.
As well as Japan, the hosts will meet Italy and Olympic champions Mexico in Group A. World and European champions Spain headline Group B alongside Uruguay, Nigeria and minnows Tahiti.
Brazil's strongest challenge is likely to come from Spain, who begin their campaign against Uruguay in Recife on Sunday.
"We still haven't won this tournament and we are here to do so," striker Fernando Torres told Spanish newspaper AS.
"That is why you are always desperate for the next tournament to arrive, to be able to win it and continue making history."
Italy and Mexico will also be in action on Sunday when they lock horns at Rio's newly refurbished Maracana in a game that should see Italian midfielder Andrea Pirlo win his 100th cap.
Some 355,000 Brazilians and foreign tourists are expected to watch games in the six host cities: Brasilia, Belo Horizonte, Fortaleza, Recife, Rio and Salvador.
State tourism agency Embratur reported on Saturday that tourism revenue across the six venues is set to be 241 million reals ($110 million, 125 million euros).
FIFA's chief medical officer, Professor Jiri Dvorak, also revealed that all doping tests conducted prior to the tournament had come back negative.