The experimental investigation herein described is aimed at understanding the effects of cellulose-based fibers on the mechanical properties of bituminous mastics for paving applications. Three bitumen (two of which modified with SBS polymers), a calcareous filler and four different types of fiber with varying content were used to prepare the investigated mastics. The filler to bitumen ratio was maintained constant. The laboratory investigations were focused on empirical tests (Needle Penetration andRing and Ball -R&B -Temperature) and dynamic-mechanical tests, the latter performed in a wide range of temperatures. Results suggest that fibers improve the M A N U S C R I P T A C C E P T E D ACCEPTED MANUSCRIPT 2 behavior of mastics for hot mix asphalts, particularly with respect to the prevention of rutting phenomena at high service temperatures.