A rekeyable lock cylinder comprises a cylinder body and a plug assembly disposed within the cylinder body. The plug assembly comprises a plug body, a plurality of pin assemblies and a guide bar. The plug body has a longitudinal axis, a transverse axis perpendicular to the longitudinal axis and a tool-receiving hole. Each of the pin assemblies is movably disposed in the plug body and comprises a first rack component and a second rack component selectively engaging with the first rack component. The guide bar is coupled to the plug body and has a plurality of pin runners for engaging with the first rack components and a tool-receiving portion exposed by the tool-receiving hole. The guide bar is capable of moving along transverse axis-direction of the plug body to disengage the first rack components from the second rack components.