A nail enamel applicator includes a resilient tube, an adaptor mounted on the top portion of the tube and having an upper end provided with a clamping hole and a guide portion, a pen head mounted in the adaptor and having an upper end provided with a tip extending through the guide portion into the clamping hole, a top cap mounted on the adaptor to cover the tip, and a brush having an upper end provided with a pipe inserted into an open lower end of the pen head and a lower end provided with multiple bristles. Thus, the tip is clamped by the clamping hole so that the clamping hole is sealed closely by the tip without producing a gap between the tip and the clamping hole to prevent air from being introduced into the tube.