Nencini also won the Mountains Jersey in 1957 Tour de France.
Nencini won the 1957 Giro d’Italia in front of Louison Bobet of France and Ercole Baldini of Italy.
Nencini was also 2nd in the 1960 Giro d'Italia behind Jacques Anquetil of France.
In addition, Nencini was 3rd in the 1955 Giro d'Italia behind Fiorenzo Magni and Fausto Coppi of Italy.
Nencini also won the Mountains Jersey in the 1955 Giro d'Italia.
In the World Championship Road Race, Nencini was 4th in 1955 behind Stan Ockers of Belgium, J-P Schmitz of Luxembourg, and Germain Derycke of Belgium.