There is disclosed a tool (102) for forming a composite component having a curved body and an integral flange from a pre-form (200), the tool comprising: a curved body portion 104 having a lay-up surface (110); and a forming assembly (105) having a lay-up configuration and a forming configuration. The forming assembly comprises: a plurality of forming elements (106) each having a lay-up surface (120) and a primary flange-forming surface (122), the forming elements (106) being radially outwardly moveable between the lay-up configuration and the forming configuration, in which the forming elements are circumferentially spaced from one another; and a plurality of filler elements (107) each having a secondary flange-forming surface (156), the filler elements (107) being arranged to move into the circumferential gaps between the forming elements in the forming configuration so as to form a substantially continuous flange-forming surface. In use a pre-form (200) is disposed on the layup surfaces of the curved body portion (104) and the forming elements (106), and movement to the forming configuration causes the pre-form (200) to be deformed between the continuous flange-forming surface and a counteracting forming surface to form the integral flange (210).