A securement device includes a simply-structured retention mechanism that permits a portion of a catheter hub or a similar medical article to be easily anchored to a patient, without the use of tape or needles and suturing. A unitary retainer desirably includes a base defining a locator mechanism. The locator mechanism interacts with a fitting of the medical device so as to position the medical device relative to the retainer. The locator mechanism also desirably guides the medical device fitting into contact with an adhesive member mounted on an outer surface of the retainer. In one form, the locator mechanism includes one or more posts that engage mating holes defined in the medical device fitting. In other forms, the locator mechanism includes a cradle defining an arcuate channel to receive a convex surface of the medical device, or a recess shaped to matingly receive the fitting. The retainer is attached to a flexible anchor pad that includes an adhesive bottom surface, which can be attached to the patient's skin. In use, a health care provider positions the medical device fitting on the retainer in a position established and guided by the locator mechanism, and attaches the fitting to the retainer via the adhesive member.