The 19-year-old winger has flown in to London to discuss terms and complete a £4.7million move from Atletico Paranaense.
The Premier League leaders have agreed a fee rising to £4.7million for the 19-year-old winger and are confident of announcing the deal this week.
Nathan began the first stage of his Chelsea medical on Tuesday after being granted permission by his club Atletico Paranaense to fly to London to discuss personal terms.
The teenager is regarded as one of the most exciting young players in Brazil and has been closely monitored by leading Premier League clubs after rising to prominence with his performances in the World Under-17 Championships two years ago.
He can play in any of the three attacking positions behind the central striker, although he has generally been used on the flanks. Reports in Brazil say that his form has dipped amid contract issues with Atletico Paranaense.
At Chelsea, Nathan is set to link up with the club's strong Brazilian contingent, with Willian, Ramires, Oscar and Filipe Luis all in the first-team squad and Lucas Piazon, 21, on loan at Eintracht Frankfurt.