Pablo Lavaselli initially excelled as a tennis player, dedicating much of his youth to the sport. As he approached adulthood, his enthusiasm for tennis diminished, prompting him to explore mixed martial arts (MMA) at age 17. Training at an MMA gym in Buenos Aires, Argentina, Lavaselli quickly gravitated toward grappling techniques over striking. Recognizing his affinity for ground combat, he transitioned fully into Brazilian Jiu-Jitsu, beginning his formal training at Team 360 under coach Eduardo Amarante.

After earning his blue belt, Pablo Lavaselli parted ways with his academy due to personal differences. Embracing an unconventional path, he established a dedicated home-based training environment in Buenos Aires, complete with mats and regular sparring sessions alongside close training partners. Despite the absence of formal coaching, Lavaselli independently crafted a disciplined and structured training methodology, systematically progressing from blue belt to black belt. This self-directed approach laid a solid foundation for his future international success.

While training independently, Lavaselli connected with Eduardo Duarte and Miguel Alderete of Nova União, who oversaw his belt promotions. Duarte awarded Lavaselli his black belt on August 3, 2019. In early 2020, Lavaselli accepted an invitation from André Porfirio to train in Orlando, Florida, supported by the "Projeto Agora" scholarship program initiated by Patrick Cooligan. This opportunity provided him access to elite-level training at Renzo Gracie Academy Orlando and previously at Cícero Costha's PSLPB Academy in São Paulo, Brazil, significantly elevating his competitive performance.

Pablo Lavaselli has consistently broken new ground for Argentine Brazilian Jiu-Jitsu. In 2021, he became the first Argentine athlete to claim an Abu Dhabi World Pro title at black belt, securing victories at both the April and November editions of the 2021 Abu Dhabi World Professional Jiu-Jitsu Championship. He continued making history in 2022 by becoming the first Argentine to win the Brazilian National Championship (Brasileiro). Additionally, his silver medal at the 2023 Pan Jiu-Jitsu IBJJF Championship marked Argentina's first podium finish at the Pan Championship at black belt in many years.

Known for his versatile and strategic grappling style, Pablo Lavaselli excels in both gi and no-gi formats. His adaptability and tactical awareness have led to significant victories over elite competitors, including Gianni Grippo, Johnny Tama, Gilson Nunes, and Diego Ramalho. Demonstrating his technical versatility, Lavaselli captured gold medals across major international circuits, notably winning the IBJJF American Nationals and the AJP South America Continental Pro in 2022.

In late 2022, Pablo Lavaselli strategically relocated his training base to California, joining the renowned Art of Jiu-Jitsu academy (AOJ) under the guidance of the Mendes brothers. Representing AOJ at major international events, including the European Championship in Paris in early 2025, Lavaselli leveraged AOJ's world-class training environment to further refine his competitive skills. This strategic move marked a significant advancement in his career, aligning him with one of the most prestigious competition teams in Brazilian Jiu-Jitsu.