The present invention relates to a method for estimating the side slip angle (βstim) of a four-wheeled vehicle, comprising: —detecting signals representing the vehicle longitudinal acceleration (Ax), lateral acceleration (Ay), vertical acceleration (Az), yaw rate (formula I), roll rate (formula II), wheels speeds (VFL, VFR, VRL, VRR); —pre-treating (1) said signals in order to correct measurement errors and/or noises, so to obtain corrected measurements of at least the longitudinal acceleration (ax), the lateral acceleration (ay), the yaw rate (formula I) and the wheels speeds (νFL, νFR, νRL, νRR), —determining (2) an estimated vehicle longitudinal speed (Vxstim) on the basis of at least one of the corrected measurements of the wheel speeds (νFL, νFR, νRL, νRR); —determining a yaw acceleration (formula III) from the signal representing the yaw rate (formula I); —solving (25) a time-depending parametrical non-linear filter, such as a Kalman filter or a Luenberger filter, describing the vehicle longitudinal and lateral speeds (formula IV) and longitudinal and lateral accelerations (formula V) as a function of the corrected measurements of the longitudinal acceleration (ax), of the lateral acceleration (ay), of the yaw rate (formula I) and the estimated vehicle longitudinal speed (Vxstim) and of a filter parameter (F) depending from depending from at least one of the vehicle yaw acceleration (formula III), yaw rate (formula I) and lateral acceleration (ay) which adds a negative component to the lateral acceleration (formula VI) determined by the filter itself, said filter parameter (F) being selected such that said negative component reaches a maximum value when it is determined that the vehicle is moving straight on the basis of said at least one of the vehicle yaw acceleration (formula III), yaw rate (formula I) and lateral acceleration (ay); —determining the vehicle estimated side slip angle (βstim) from said longitudinal and lateral vehicle speeds (formula IV) determined by solving the non-linear filter. The present invention further relates to a computer program implementing said method, a control unit having said computer program loaded, and a vehicle comprising said control unit.