The 17-year-old has featured regularly in Abel Ferreira's senior team since making his professional debut in the middle of April.
Guilherme has already made 23 first-team appearances across all competitions, including 15 outings in the Brazilian top flight.
The teenager is also a Brazil Under-20 international and is considered as one of the latest stars to emerge from the Palmeiras youth system.
A recent report claims that Man United are keeping tabs on Guilherme, who is regarded as a potential star for the future.
However, the Red Devils could face stern competition for Guilherme's signature as journalist Fabrizio Romano claims that both Chelsea and Bayern Munich are among several clubs who are closely monitoring the midfielder.
Romano states that the West Londoners and the German champions were two of five European clubs that had scouts in attendance to watch Guilherme play as a second-half substitute in Palmeiras' 1-1 draw with Boca Juniors in the second leg of their Copa Libertadores semi-final last Friday - a game Boca Juniors went on to win 4-2 on penalties.
Palmeiras are yet to receive a formal bid from either Chelsea or Bayern, but the European duo will continue to monitor the youngster's development as they consider making their first move.
Guilherme is under contract at Palmeiras until June 2025 and is understood to possess a £52m release clause.
Chelsea have delved into the Brazilian market in recent transfer windows and they most recently recruited Deivid Washington and Angelo Gabriel from Santos this summer.
Bayern, meanwhile, focused solely on signing established senior players this summer, with Thomas Tuchel bolstering his squad with five fresh faces including the £100m addition of striker Harry Kane.
The German giants last recruited a Brazilian player four years ago when they re-signed winger Douglas Costa - now at Los Angeles Galaxy - on loan from Juventus.
A potential move from any top teams for Guilherme would most likely take place after he turns 18 in February next year.