The men, who are also being investigated for an offence against Vinicius' moral integrity, have been banned from approaching and communicating with the Real Madrid winger pending further investigation, a court statement said.
The inquiry was opened after an inflatable black effigy dressed in the shirt of Vinicius Jr was hung from a bridge in front of Real Madrid's training grounds before a match against Atletico Madrid in January.
Alongside it was a large red and white banner - the colours of Atletico - that read "Madrid hates Real".
Three of the arrested men were members of "a radical group of fans of a Madrid club" who were previously flagged during matches as "high risk", according to police.
The court said the four suspects are also banned from approaching the Real Madrid training grounds.
They will not be allowed within 1,000 metres of the Santiago Bernabeu and Civitas Metropolitano stadiums, nor any LaLiga stadium during matches.
Vinicius Jr has been in the spotlight since Sunday when racist chants were hurled at him at Valencia's Mestalla stadium.
His complaints about Spain and LaLiga not doing enough to fight racism have sparked a worldwide wave of support and a national debate in Spain.
