Neymar failed to inspire his team in a goalless draw against Flamengo in their opening match of the Brazilian championship played in the new World Cup stadium in Brazil's capital.
The 21-year-old striker, seen as one of the brightest prospects in soccer, announced on Saturday he had picked Barca over Real Madrid and would be leaving Santos to sign a five-year deal with the Catalan club.
Many of the 63,500 spectators who filled Brasilia's Mane Garrincha National Stadium were Flamengo fans who booed Neymar when he gained possession of the ball and cheered when he lost it.
The Brazilian ace with a Mohican hairdo cried during the national anthem line-up before the game, his last for the club that launched his career and where he became the top scorer since Pele.
"It was an honour to have played for this marvelous team Santos, I am so happy I did," he told reporters.
"Every child has a dream, either to be a player, a dentist or a reporter. My dream was to become a professional athlete and I have achieved that. Today Barcelona is fulfilling my dream of going to a totally beautiful team," he told Globo TV.
Some of the Flamengo fans who booed Neymar on Sunday will probably be cheering him on in the same Brasilia stadium on June 15 when he is due to play for Brazil against Japan in the opening game of the Confederations Cup, an eight-nation warm-up event for next year's World Cup.
Neymar does not know when he will travel to Barcelona but said he was excited at the prospect of playing alongside Lionel Messi, Xavi, Andres Iniesta and Dani Alves.
"The Santos fans are the only ones who have always supported me. I can only thank them and say 'see you later,' because I will be back one day," Neymar said.
Brasilia's 71,000-seat Mane Garrincha stadium, named after the nation's beloved dribbler who starred in Brazil's 1962 World Cup win in Chile, appeared to pass the test game required by FIFA, even though half the spot lights went out mid-way through the first half. The captains decided to play on and the lights were restored at half time.
Brazil's most expensive stadium ever cost 1.2 billion reais ($590.1 million) even though Brasilia has no major football team.
The city government is already looking for other uses for the arena and announced Beyonce will perform there in September.
