An optical connector assembly (1) for connecting an optical fiber (9), an optical element (4) (light-emitting element or light-receiving element), and an electric circuit together. A bolt (32) of an optical fiber-mounting fitting in which the optical fiber (9) is inserted in the hole of an elastic seal and a bolt (31), is screwed into a threaded hole formed in a housing (2) of the plug (1) that accommodates the optical element (4) in order to couple the optical fiber (9) to the plug (1). The connection between the optical element (4) and the electric circuit is accomplished by a jack (20) and the plug (1) is provided with a lock mechanism based on a push-type lever (20), featuring improved sealing performance against water, oil, dust and dirt.