The aim of this study was to determine the inter-rater reliability of the Functional Movement Screen (FMSTM) within a police population and determine whether formal training improved reliability and assessment accuracy. Police Physical Training Instructors (PTI) (n = 67) rated 98 randomised videos of officers performing four primary FMSTM tasks (overhead squat, hurdle step, in-line lunge, and rotary stability) twice within a two-day annual training program. A one-hour FMSTM training session was completed between the two assessment periods. PTI scores were compared to a Master score. The level of agreement between raters was low to moderate across all FMSTM items. The inter-rater reliability between the raters did not improve significantly following training. The level of agreement between “Rater” and “Master” scores improved significantly post-training. FMSTM subtest items have varying reliability. Staff training should be performed and compared to a Master rater prior to employing the FMSTM as an assessment tool in law enforcement.