Guilherme began his professional career at the age of 18 when he signed with Osasco Audax, a Brazilian football club based in Sao Paulo. He quickly established himself as a promising young talent and caught the attention of several European clubs. In 2016, he made a move to Europe and joined Italian Serie A side Udinese. During his time at Udinese, Guilherme gained valuable experience playing against some of the best teams in Italy and honing his skills in one of the top leagues in the world.