An intense reactivation of a large earthflow took place in Montaguto (Southern Apennines, Italy) between 2005 and 2006, with a 2÷2.5 km long run-out distance and a landslide mass thickness approximately ranging between 5 m and 30 m. The average landslide displacement rate was estimated to range between 3 and 7 m/day and important transport infrastructures were affected by large debris volumes deposited at the toe of the slope. In this work an application of the Smoothed Particle Hydrodynamics method has been carried out in order to simulate both the main features of the earthflow propagation, that is the direction and the thickness of the flowing mass, as well as to investigate some factors of the soil mechanical behavior that might have controlled the earthflow mobility. In particular, two different assumptions concerning the soil rheology, i.e. Bingham viscoplasticity and frictional-consolidating soil model, have been made for comparison purposes. Based on the experiences gained from previous authors concerning the in-situ features of similar earthflow soil masses, these landslides are thought to behave more as a viscous fluid during the very first stages of propagation due to phase transition processes and, later on, to recover a soil-like behavior due to soil consolidation processes. The SPH numerical results of the Montaguto earthflow propagation seem to be in good agreement with the field observations in terms of both movement direction, run-out distance and thickness of the debris soil mass. The modelling results confirm that these landslide processes can be efficiently modelled by means of the SPH numerical technique, providing that a soil rheology capable of taking into account the main features of the soil behavior that control the earthflow mobility is used.