A fiber optic connector includes a housing having a longitudinal passage extending therethrough and having two ends. A rear end is adapted for attaching a fiber optic cable therethrough. A front end is adapted for having a mating fiber contact plug secured thereto in the passage. The plug has a fiber-receiving passage coextensive with the passage in the housing. A retaining ring is disposed in a transverse groove in the passage in the housing for abutment against the fiber contact plug near the front end thereof to secure the plug in the passage in the housing. A tool is provided for assembling the fiber optic connector. The tool includes a head for receiving and holding the housing of the connector in position with the fiber contact plug and retaining ring insertable into the passage thereof. A pusher apparatus is mounted for movement relative to the head and is engageable with the retaining ring to push the retaining ring into the groove while the connector housing is held by the head of the tool.