For producing a joined-together fiber composite component in which mutually adjacent regions (5, 6) are constructed in different ways but are cured in a joint thermal treatment, arranged between the regions is a transitional film (8), which has a composition that differs from the compositions of the matrices of the two adjacent regions (5, 6) and which spatially separates the two adjacent regions (5, 6) in the joint thermal treatment but enters into permanent bonds with the matrices of the two adjacent regions (5, 6). The fact that the transitional film (8) is vacuumtight means that one adjacent region (5) can first be formed independently from a preform (9) and enclosed with the transitional film (8), thereby bounding certain portions, and be evacuated and infiltrated with resin (22) on its own, and the other adjacent region (6) can be formed from a prepreg (2). Following this, the two adjacent regions (5 and 6) are brought together and joined to each other, the other adjacent region (6) being sealed and the other adjacent region (6) being evacuated during the subsequent joint thermal treatment for the removal of excess air.