A connector attached optical fiber unit includes: an MT optical connector which includes a joining end surface formed at a front end of the MT optical connector and a hollow portion opened to a rear end surface opposite to the joining end surface; a tubular boot which includes a front end insertion portion inserted and fixed into to the hollow portion and a tube attachment portion formed at a rear end portion of the tubular boot, the tubular boot extending to a rear side from the MT optical connector; a protection tube into which the tube attachment portion is inserted and to which the tube attachment portion is fixed; and a plurality of optical fibers which include tip portions inserted and fixed into the MT optical connector and are accommodated inside the boot and the protection tube.