The 33-year-old was limited to just 10 matches for Botafogo after joining the Rio de Janeiro outfit from Shandong Luneng in January.
“I’m not going to die a slow death. It’s over. Finished,” Montillo told a press conference on Thursday.
“Unfortunately my body was telling me that I’m not going to get back to 100% fitness. It’s the right moment to go. I’m sure that this is the best decision for me and the club.”
Montillo was capped six times for Argentina’s national team after also representing his country at youth level.