An optical connector plug is comprised of a pair of divided front and rear housings formed generally in a quadrilateral tubular shape for receiving a ferrule to hold an optical fiber. A housing, one of the housings is provided with engagement openings on at least opposite wall portions thereof, and the other housing is provided with engagement projections on its opposite wall portions to be engaged in the engagement openings. Furthermore, fitting projections are formed in the longitudinal direction on the wall portions in which the engagement openings are formed, and fitting recesses to be fitted with the fitting projections are formed in the wall portions on which the engagement projections are formed. The pair of housings are firmly joined to each other by engaging the engagement projections with the engagement openings and by fitting and engaging the fitting projections in the fitting recesses.