Senegal midfielder Salif Sane, 22, who joined Nancy in 2011, is to join German top-flight team Hannover 96.
"It's signed. The transfer will bring us two million euros," a source at the French club who declined to be identified told Reuters on Thursday.
Nancy were relegated to Ligue 2 last weekend after finishing third from bottom.
Hannover ended up ninth in the Bundesliga last season.