With the fundamental help of Andre Weil and Oscar Zariski, members of the Bourbaki group that, by the end of the second world war, were working at the University of São Paulo, and with the participation of some Brazilian mathematicians, the Mathematical Society of Mathematics of São Paulo was founded in 1945. Being the first mathematics society in the country, and staying unique for some years, the Society of Mathematics of São Paulo increased and assumed national relevance, until their members decided to close their activities and to found a national society. The Brazilian Society of Mathematics was founded in 1969. In this talk we will contextualize the transition of the regional society to the national society, focusing their first academic activities, emphasising the Brazilian Colloquium of Mathematics and the first publications of this society.