Striker Nilmar opened the scoring in the fourth minute and Oman midfielder Hassan Ghailani headed into his own goal just past the hour.
Playing with the same team that beat England 1-0 in Doha on Saturday, the Copa America and Confederations Cup holders dominated possession but were denied several chances by Omani goalkeeper Ali Al-Habsi.
The home side did not sit back a defend, creating a good chance in the second minute when Hassan Rabbea shot into the side netting.
Two minutes later Brazil were in front. Luis Fabiano's shot was parried by the keeper and Nilmar netted the rebound for his second goal in four days after scoring against England.
"It's always good to score goals, to play, to get opportunities (in the national team). I'm trying to make the most of it," the 25-year-old Nilmar, who was standing in for the injured Robinho.
Brazil's victories this year included beating former world champions Italy, twice, Argentina, Uruguay and England. They finished top of the 10-nation South American World Cup qualifying group.
"It was a good season, we finished the year with another victory. I'm happy to finish the season this way," said Kaka, who only played in the first half.
"I think that now there are just some details missing to correct until the World Cup but next year a lot of things are going to happen before the tournament."
