Nathan is undergoing a medical at Stamford Bridge after the Premier League leaders reportedly agreed a deal worth ??4.5m to beat off interest from Manchester City, Arsenal and Liverpool.
The 19-year-old youth international broke through the ranks with Atletico Paranaense but has become embroiled in a legal battle with the Brazilian Serie A side and as a result is out of contract at the end of the month.
Nathan burst on the scene??in the FIFA U17 World Cup in 2013 when he scored five goals to help Brazil reach the quarter-finals.
He has since progressed to the U20 side and has notched up five appearances.
The teenager is expected to return to Brazil before becoming the seventh Brazilian player at Chelsea full time in June.