Background: Although the reliability of determining acromial morphology has been examined, to date, there has not been an analysis of interobserver and intraobserver reliability on determining the presence and measuring the size of an acromial enthesophyte. Questions/Purposes: The hypothesis of this study was that there will be poor intraobserver and interobserver reliability in the (1) determination of the presence of an acromial enthesophyte, (2) determination of the size of an acromial enthesophyte, and (3) determination of acromial morphology. Patients and Methods: Fifteen fellowship-trained orthopedic shoulder surgeons reviewed the radiographs of 15 patients at two different intervals. Measurement of acromial enthesophytes was performed using two techniques: (1) enthesophyte length and (2) enthesophyte-humeral distance. Acromial morphology was also determined. Interobserver and intraobserver agreement was determined using intraclass correlation and kappa statistical methods. Results: The interobserver reliability was fair to moderate and the intraobserver reliability moderate for determining the presence of an acromial enthesophyte. The measurement of the enthesophyte length showed poor interobserver and intraobserver reliability. The measurement of the enthesophyte-humeral distance showed poor interobserver reliability and moderate intraobserver reliability. The interobserver and intraobserver reliability in determining acromial morphology was found to be moderate and good, respectively. Conclusions: There is fair to moderate reliability among fellowship-trained shoulder surgeons in determining the presence of an acromial enthesophyte. However, there is poor reliability among observers in measuring the size of the enthesophyte. This study suggests that the enthesophyte-humeral distance may be more reliable than the enthesophyte length when measuring the size of the enthesophyte.