He made his debut for Monaco, starting the whole game, and kept a clean sheet, in a 1–0 win against Canet Roussillon in the third round of the Coupe de France. In his first two league games for the club, Naldo received a red card when he was sent off twice in seven days against Strasbourg and Dijon. Even after serving his suspensions, he remained out of the starting line–up for the next three months. Naldo didn’t make an appearance until on 1 May 2019, coming on as a 63rd minute substitute, in a 2–2 draw against Rennes. Following this, he had a first team run ins that saw AS Monaco avoided relegation. At the end of the 2018–19 season, Naldo went on to make nine appearances in all competitions.