The Soyuz TMA-8 carrying Marco Pontes - travelling with Pavel Vinogradov, a Russian, and Jeffrey Williams, an American - docked automatically with the ISS at 0419 GMT.
Pontes was the first of three to enter the ISS, after the door was opened at 0559 GMT, followed by Vinogradov and Williams.
Traditionally it is the head of mission, in this case Vinogradov, who enters first.
The Brazilian carried his country's flag and smiled broadly as he joined William MacArthur, an American, and Valery Tokarev, a Russian, who have been on the ISS since October 2005.
The new crew members had blasted off from Baikonur cosmodrome in Kazakhstan on Thursday.
Pontes, a 43-year-old Brazilian air force officer, returns to Earth on April 9. Vinogradov and Williams are to spend six months on the ISS, the only space station operating since the closure of Russia's Mir orbiter in 2001.
They will prepare for the arrival of a US space shuttle carrying Thomas Reiter, a German who will be the first European to make an extended stay on the ISS.
During the mission, Pontes will carry out scientific experiments, some of them in the field of nanotechnology. He will also examine Brazil's surface from space.
The docking was greeted by applause at the control centre, where a number of Brazilians were also present.
Raimundo Mussi, a representative of Brazil's space agency, said: "I am very happy and grateful that everything went so perfectly."
Updated mission details, video and pictures can be found at Nasa's ISS page here: http://www.nasa.gov/mission_pages/station/main/index.html