A magnetic field sensor has a magnet (M1) that produces a magnetic field with a magnetic field axis (f), has a magnet axis (a) and is held in a component (4) that can move about at least one axis and has a component axis (b). Also a method for mounting a magnet (M1) of a magnetic field sensor. The magnet (M1) is held in the component (4) in such a manner that the magnetic field axis (f) coincides, as closely as possible, with the component axis (b). A deviation of the magnetic field axis (f) from the magnet axis (a) is measured, and the angle of deviation (α) is corrected during the mounting of the magnet (M1) in the component (4).