Yamasaki was born in São Paulo, Brazil, the oldest of two sons born to Shigeru Yamasaki. Yamasaki’s family has been teaching martial arts in Brazil for two generations. His father is half-Japanese. Yamasaki and his younger brother Fernando, a 6th degree Black Belt in BJJ, originally began training in judo as children under their father Shigeru, an 8th degree Red/White belt in the art and their uncle Shigueto Yamasaki. In 1986, at the age of 22 Yamasaki began training in Brazilian jiu-jitsu under 5th degreeblack belt Marcelo Behring, who began teaching jiu-jitsu at the same gym in São Paulo where Yamasaki taught judo. Yamasaki’s training under Behring would only last a short time as he would soon move to the United States, traveling frequently back to Brazil to continue his jiu-jitsu training under Behring, until the latter switched gyms. Yamasaki would continue his training in jiu-jitsu under his brother Fernando, who had begun training under Otavio de Almeida and Roberto Lage. On January 2002, Otavio de Almeida, president of the Federação de Jiu-Jitsu Brasileiro de São Paulo, Brasil promoted Yamasaki to 4th degree black belt.
UFC career
Yamasaki first became affiliated with the UFC, when both he and his brother helped the promotion organize their first event in Brazil, UFC Brazil: Ultimate Brazil in São Paulo. After the event, Yamasaki asked UFC referee 'Big' John McCarthy if there were any referee positions available with the company, and was told that the company was looking for someone, marking the beginning of Yamasaki's career as an MMA referee. At UFC 142 Yamasaki controversially disqualified Erick Silva for illegal blows to the head of Carlo Prater. After the bout, in-ring announcer Joe Rogan criticized Yamasaki for making a bad decision. The UFC upheld his decision and did not seek appeal. At, Yamasaki was criticized by observers, including Dana White, after he failed to stop a fight between Valentina Shevchenko and Priscila Cachoeira: Shevchenko landed over two hundred strikes to Cachoeira's three. Dana White has previously repeatedly called for Yamasaki to be precluded from refereeing future UFC events, due to similar controversies. Since the event, Yamasaki has not applied for any UFC refereeing jobs although he has refereed a few other organizations' events.
Personal
Yamasaki lives between São Paulo, Brazil, and Bethesda, Maryland, with his wife and children, where he co-owns and operates a chain of Brazilian jiu-jitsu schools. Yamasaki also owns a construction company in the United States. Yamasaki comes from a martial arts family. Both his father Shigueru Yamasaki and uncle Shigueto Yamasaki are high ranking judoka in Brazil. His brother Fernando Yamasaki holds black belt ranks in both Brazilian jiu-jitsu and judo. His cousin Shigueto Yamasaki, Jr. is also a judoka who represented Brazil at the 1992 Summer Olympics.
