Born in Brazil in 1988, Guilherme Mendes began his Brazilian Jiu-Jitsu journey in 2001 alongside his brother, Rafael Mendes. Initially introduced to the art by their cousin, the Mendes brothers soon transitioned to training under renowned instructors Ramon Lemos and Leonardo Santos, who significantly shaped their early development.

Guilherme quickly established himself as a dominant force in the Peso Pluma (64 kg) division, securing four IBJJF World Championship titles (2009, 2011, 2012, and 2014). Known for his precise guard play, fluid transitions, and strategic mindset, Guilherme consistently outmaneuvered opponents at the highest levels. On May 19, 2015, immediately following his fourth world title victory, Guilherme announced his retirement from professional competition at just 26 years old. Driven by a desire to fully dedicate himself to coaching and family life, he stepped away from competition at the peak of his athletic career.

In 2012, Guilherme co-founded the Art of Jiu-Jitsu (AOJ) academy in California alongside his brother Rafael Mendes. Initially affiliated with the prestigious Atos Jiu-Jitsu academy led by André Galvão and Angelica Galvão, AOJ became an independent entity in 2020. By 2024, the Mendes brothers expanded their academy, opening a second AOJ facility and growing their affiliation network. Guilherme personally oversees instructor training, ensuring AOJ's culture and technical standards remain consistent across all locations. He remains actively involved at AOJ headquarters, teaching classes, rolling with students, and providing detailed, individualized feedback daily.

Since retiring from competition in 2015, Guilherme Mendes has played a pivotal role in developing AOJ's structured training curriculum. Under his guidance, classes are systematically divided into fundamental, advanced, and competition modules. Guilherme emphasizes precise drilling sequences, transitional positioning, and the critical "connection" between techniques. This meticulous approach has produced athletes recognized for their systematic and identifiable styles, clearly reflecting the Mendes brothers' technical influence.

A cornerstone of Guilherme's legacy is the AOJ kids' program, which he nurtured from the academy's inception. Widely regarded as one of the strongest youth teams in Brazilian Jiu-Jitsu, AOJ reached a significant milestone in 2020 when its first generation of youth athletes graduated to black belt and elite competition. Notably, Jessa Khan became the first AOJ youth athlete to earn a black belt entirely through the AOJ system, subsequently capturing an IBJJF world title. Other elite competitors, such as Tainan Dalpra, also emerged from AOJ's junior ranks, underscoring Guilherme's exceptional ability to cultivate teenage grapplers into world-class adult competitors.

Guilherme Mendes is renowned for his thoughtful and continually evolving coaching philosophy. He advocates the principle "posture first, technique second," emphasizing that proper posture and positioning are foundational for effective technique execution. Guilherme actively studies successful coaches both within and outside Brazilian Jiu-Jitsu, continuously refining his teaching methods. Recognizing the rising prominence of no-gi competition, he has adapted AOJ's curriculum to incorporate increased wrestling and leg-lock defense, ensuring the academy remains at the forefront of competitive trends.

Widely recognized as one of the top coaches in Brazilian Jiu-Jitsu, Guilherme Mendes is frequently mentioned alongside esteemed figures such as John Danaher for his systematic and analytical approach. AOJ athletes are noted for their technical innovations and structured gameplans, clearly reflecting Guilherme's coaching influence. In 2022, an industry publication named Guilherme and Rafael Mendes among the best coaches of the year, highlighting their success in developing homegrown champions and innovative training methodologies. Guilherme's legacy is defined by the consistent success of AOJ athletes and his significant contributions to modernizing training practices.

Outside the academy, Guilherme Mendes places significant emphasis on family life. Married with two young children, he frequently highlights the importance of balancing family responsibilities with running a successful academy. Guilherme credits fatherhood with enhancing his patience and communication skills, positively influencing his coaching of both children and adults. Reflecting on his early retirement, Guilherme expresses no regrets, finding fulfillment in witnessing his students achieve success on the world stage. He continues to share insights from his personal and professional journey through media appearances, seminars, and podcasts, further solidifying his influential role in shaping the future of Brazilian Jiu-Jitsu.