This research is a study about the Anti-Japanese sentiment in Brazil. The Anti-Japanese sentiment involves actions, ideologies and various types of public demonstrations of hostility towards Japanese people and their descendents. The goal is to investigate the presence of the Anti-Japanese sentiment at the Constituent Convention that took place in 1933-1934. It was in a place that was dedicated to produce a new Constitution that some Brazilian intellectuals saw the opportunity to create laws in order to interrupt the Japanese immigration to Brazil. The research identifies the influence of the medical-scientific theories on the Anti-Japanese arguments that ranged from the biological to the moral aspects in order to disqualify the Japanese immigrant. These scientific speeches gained a political shape at the Constituent Convention and, by the end, the Japanese immigrant was considered unassimilable. The main purpose of this research is to understand how these arguments were built and how they were used by these constituents as a political statement.