LaLiga reported racist insults aimed at Vinicius Junior ahead of a league match last week at Getafe's stadium to Spanish prosecutors on Tuesday.
The Spanish topflight told AFP they had made the legal complaint after some fans yelled "Vinicius, monkey" outside the Coliseum Alfonso Perez stadium, before Madrid's 2-0 victory.
Vinicius, 23, has become a symbol of the fight against discrimination in Spanish football after suffering racist abuse on many occasions.
Most notably in May 2023 Vinicius remonstrated with a supporter at Valencia's Mestalla stadium after he was racially abused.
Real Madrid coach Carlo Ancelotti said in November the player has become "unfortunately used to" racism in Spain.
Spain will face Brazil at Madrid's Santiago Bernabeu stadium in a friendly on March 26, arranged to "strengthen the commitment against violence and racism in football".
Earlier on Tuesday, LaLiga reported alleged racial abuse of Sevilla's Morocco striker Youssef En-Nesyri from his team's 2-1 win at Rayo Vallecano on Monday.