Method for the aluminothermic welding of rails, involving the steps of: - triggering an aluminothermic reaction in a crucible (2), - pouring the metal resulting from said reaction into the mould (1) so as to fill the moulding cavity from the rail flange, - after filling the cavity, triggering a second aluminothermic reaction above the rail head, and pouring the metal resulting from said reaction into the cavity in the region of the rail head. The mould (1) used in the method is designed to fit over the ends of two rails to form a moulding cavity (10) comprising a crucible (4) positioned above the rail head region so that it can be fed with molten metal of the cavity (10) via a secondary passage (42).