Smith, CA, Chimera, NJ, Wright, NJ, and Warren, M. Interrater and intrarater reliability of the functional movement screen. J Strength Cond Res 27(4): 982–987, 2013—The purpose of this study was to investigate interrater and intrarater reliability of the Functional Movement Screen (FMS) with real-time administration with raters of different educational background and experience. The FMS was assessed with real-time administration in healthy injury-free men and women and included a certified FMS rater for comparison with other raters. A relatively new tool, the FMS, was developed to screen 7 individual movement patterns to classify subjects' injury risk. Previous reliability studies have been published with only one investigating intrarater reliability. These studies had limitations in study design and clinical applicability such as the use of only video to rate or the use of raters without comparison to a certified FMS rater. Raters (n = 4) with varying degrees of FMS experience and educational levels underwent a 2-hour FMS training session. Subjects (n = 19) were rated during 2 sessions, 1 week apart, using standard FMS protocol and equipment. Interrater reliability was good for session 1 (intraclass correlation coefficient [ICC] = 0.89) and for session 2 (ICC = 0.87). The individual FMS movements showed hurdle step as the least reliable (ICC = 0.30 for session 1 and 0.35 for session 2), whereas the most reliable was shoulder mobility (ICC = 0.98 for session 1 and 0.96 for session 2). Intrarater reliability was good for all raters (ICC = 0.81–0.91), with similar ICC regardless of education or previous experience with FMS. The results showed that the FMS could be consistently scored by people with varying degrees of experience with the FMS after a 2-hour training session. Intrarater reliability was not increased with FMS certification.