A tamper evident plastic closure for vials for storing substances for medical or pharmaceutical applications having a neck with a flange at an axial end thereof, for holding a plug in a mouth of a vial, said plastic closure comprising: a tubular locking body having a distal end and a proximal end and being configured to be mounted at the neck of the vial, and a cap coupled with the tubular locking body at the distal end; wherein the tubular locking body comprises: a retaining member provided at the distal end, configured for retaining the plug to be held in the mouth of the vial, wherein a central opening is formed in the retaining member for providing access from the outside of the tubular locking body to the inside of the vial via the plug; and wherein the cap comprises: a disc-shaped cover for covering the distal end of the tubular locking body and covering the central opening of the tubular locking body, and a coupling portion (28, 30, 32) provided at a center of the disc-shaped cover and protruding from a bottom surface thereof, for coupling the cap with the tubular locking body by positive-fit engagement of the coupling portion (28, 30, 32) with the central opening of the tubular locking body; wherein the cap and the tubular locking body are formed as separate members, and the tubular locking body is formed as a single-piece sleeve configured to cover the entire region of the neck of the vial; characterized in that the tubular locking body is configured to be mounted at the neck of the vial by locking, wherein the coupling portion comprises an annular frangible portion integrally formed with the disc-shaped cover and protruding from the bottom surface of the disc-shaped cover, a cylindrical protrusion protruding from the bottom surface of the disc-shaped cover and an indicator ring, wherein the cylindrical protrusion and the indicator ring are connected with each other via the annular frangible portion and configured such that after removal of the cap from the distal end of the tubular locking body by irreversibly breaking the annular frangible portion for providing access to the inside of the vial via the plug, the indicator ring remains as a tamper evidence at a rim of the central opening of the tubular locking body that is clamped or held with axial play between the bottom of the retaining member and an upper surface of the plug and protrudes in radial direction inward beyond the rim of the central opening of the tubular locking body into the central opening. a tubular locking body having a distal end and a proximal end and being configured to be mounted at the neck of the vial, and a cap coupled with the tubular locking body at the distal end; wherein the tubular locking body comprises: a retaining member provided at the distal end, configured for retaining the plug to be held in the mouth of the vial, wherein a central opening is formed in the retaining member for providing access from the outside of the tubular locking body to the inside of the vial via the plug; and wherein the cap comprises: a disc-shaped cover for covering the distal end of the tubular locking body and covering the central opening of the tubular locking body, and a coupling portion (28, 30, 32) provided at a center of the disc-shaped cover and protruding from a bottom surface thereof, for coupling the cap with the tubular locking body by positive-fit engagement of the coupling portion (28, 30, 32) with the central opening of the tubular locking body; wherein a disc-shaped cover for covering the distal end of the tubular locking body and covering the central opening of the tubular locking body, and a coupling portion (28, 30, 32) provided at a center of the disc-shaped cover and protruding from a bottom surface thereof, for coupling the cap with the tubular locking body by positive-fit engagement of the coupling portion (28, 30, 32) with the central opening of the tubular locking body; wherein the cap and the tubular locking body are formed as separate members, and the tubular locking body is formed as a single-piece sleeve configured to cover the entire region of the neck of the vial; characterized in that the tubular locking body is configured to be mounted at the neck of the vial by locking, wherein the coupling portion comprises an annular frangible portion integrally formed with the disc-shaped cover and protruding from the bottom surface of the disc-shaped cover, a cylindrical protrusion protruding from the bottom surface of the disc-shaped cover and an indicator ring, wherein the cylindrical protrusion and the indicator ring are connected with each other via the annular frangible portion and configured such that after removal of the cap from the distal end of the tubular locking body by irreversibly breaking the annular frangible portion for providing access to the inside of the vial via the plug, the indicator ring remains as a tamper evidence at a rim of the central opening of the tubular locking body that is clamped or held with axial play between the bottom of the retaining member and an upper surface of the plug and protrudes in radial direction inward beyond the rim of the central opening of the tubular locking body into the central opening.