A leak proof needleless medical connector has a housing, an actuator, a resilient member and an adapter. The housing includes a valve tube. The valve tube has a bottom annular blocking projection extending from an inner surface thereof. The actuator and the resilient member are mounted in the housing and the adapter is mounted on a top of the housing. A bottom valve stem is mounted in the valve tube of the housing. A gap is formed between the bottom valve stem and the valve tube. A bottom end of the bottom valve stem abuts the bottom annular blocking projection of the valve tube to close an open bottom of the valve tube. In use, a dosing unit is screwed into the needleless medical connector. Thus, a flow channel is formed within the needleless medical connector and the dosing unit to allow passage of medication.