An improved catheter securement device, the device having a main body assembly for securing a catheter housing, the assembly adapted to adhesively adher to the skin of a patient, wherein the improvement is a thin, flexible base extension member that is adapted to adher to the patient's skin, the base extension member being provided with an elongated slit dividing the base extension member into two leg portions. The catheter securement device is adhered to the patient such that the venous catheter portion extends through the slit at the insertion site when the catheter housing is properly retained. Preferably, the adhesive utilized to adhere the base extension member to the patient's skin incorporates an anti-microbial composition to combat microorganisms in the area of the insertion site.