A portal access assembly includes an inserter that has a needle, a cap moveable along the length of the needle and an infuser having a cannula through which the needle extends. A safety mechanism inside the cap allows the needle to be moved relative to the cap so long as the shaft of the needle biases against an edge of one of the legs of the mechanism. After the cannula is properly positioned in the implanted port to establish a fluid path between the port and the infuser, the needle is removed by being pulled upwards until it no longer biases the one leg of the mechanism. At which time the safety mechanism fixedly captures the needle inside the cap to prevent the contaminated tip of the needle from being exposed to the environment. At the same time, the cap is detached from the infuser.