The 23-year-old appeared to be targeted by a child during Los Blancos' 2-2 draw with Valencia at Mestalla at the weekend, where his brace rescued a point for Carlo Ancelotti's side.
A video posted on social media shows a young child - who is sitting on the lap of a woman and has their face obscured - yelling the word 'mono', which translates to m in English.
The person whose lap the child is sitting on quickly notices the person filming and attempts to stop them from doing so, and the woman who recorded the footage spoke with ESPN Brasil after the game.
The woman revealed that the police had been called to the stadium, and according to The Athletic, La Liga have now launched their own investigation into the incident, which comes just 10 months on from previous racial abuse towards Vinicius.
During Real's away game with Valencia in May 2023, Vinicius drew the referee's attention to racism coming from Valencia supporters, three of whom were identified by the home club and banned from the stadium.
However, a report from the Spanish Football Federation stated that "hundreds" of supporters were racially abusing Vinicius prior to kickoff last season, and Los Che were given a five-game stadium closure, which was reduced to three on appeal.
Vinicius - who was sent off in injury time during last season's meeting with Valencia at Mestalla - claimed that "racism is normal" in La Liga after the game, and Real Madrid reported the abuse as a hate crime to the Spanish Attorney General's Office.
In between their two most recent games with Real Madrid at Mestalla, Valencia reportedly worked in close collaboration with La Liga to minimise the risk of future incidents of racist abuse and ensure swift action if any allegations were made.
Real hosted Valencia at the Bernabeu back in November, where Vinicius notched another pair of goals in a 5-1 win, and there were no accusations of racist abuse directed towards the Brazil international or any players on that occasion.
Vinicius's brace on Saturday came after Real Madrid had fallen 2-0 down thanks to goals from Hugo Duro and Roman Yaremchuk, but the contest descended into chaos at the full-time whistle.
Deep into injury time, Jude Bellingham met Brahim Diaz's delivery and headed home to ostensibly complete a stunning comeback from the visitors, but Gil Manzano's whistle had blown as Diaz sent his cross into the box.
Furious Real Madrid players immediately swarmed Manzano, but their pleas fell on deaf ears, and the official also gave Bellingham a straight red card for something that the Englishman said in the commotion.
Real Madrid and manager Ancelotti slammed Manzano's "unprecedented" decision, but a draw was good enough for Los Blancos to open up a seven-point lead over Girona at the top of the La Liga table.
Real are back in action on Wednesday night, hosting RB Leipzig in the second leg of their Champions League last-16 tie after a 1-0 win at the Red Bull Arena in their opening battle.