Abstract: Disclosed are various embodiments of a secure composite fastener. In some embodiments, a threaded inner core is formed of a polymeric based composite and is surrounded by an outer portion formed of a different polymeric composite that has a high resistance to permanent mechanical deformation. The fastener can have a threaded bore located centrally and extending axially therethrough. The diameter of the threaded bore is reduced in the section of the bore that extends through the outer portion. The reduction in diameter can form a locking portion.