The Rio Ave midfielder is the latest player to sign for the ambitious Ligue 1 outfit as they prepare for the 2018-19 season
Monaco continue to build towards the 2018-19 Ligue 1 season by completing the signing of Pele.
The 26-year-old joins from Rio Ave and is likely to replace Fabinho following the midfielder's move to Liverpool.
Pele, a Guinea-Bissau international, won Rio Ave's player of the season award last campaign.
"I am very happy to join Monaco, an ambitious club competing in the Champions League and a contender in Ligue 1," Pele told the club's official website.
"It's great motivation and a dream to represent Monaco. I cannot wait to meet the staff and my team-mates."
Although Fabinho and Thomas Lemar have left the club, Monaco have made signings including Barcelona teenager Robert Navarro and Chelsea youth prospect Jonathan Panzo for the new season.
They follow Monaco's signing of Willem Geubbels, a France Under-17 international who joined in a €20 million (£18m/£23m) deal from Lyon in June.