A method for manufacturing a one-piece reinforced structure and obtained structure is provided, the method using base components made of partially-cured composite material and joining the base components together, applying a coating made of composite material on the base components, and applying heat on the assembly formed by the base components covered with the coating until a complete curing of the assembly is obtained, such that a one-piece reinforced structure made of composite material is obtained formed by the coating and the base components adhered to the coating, wherein the base components that form part of the very manufactured structure act as a mould during the manufacturing process, thus preventing the need to use moulds on which the composite material is deposited that must be subsequently removed from the final obtained structure.