Purpose/Hypothesis: Observation of muscle coordination is a common part of a pelvic floor muscle examination; however, no observation tool is currently available to facilitate a clinician's objective documentation of pelvic floor muscle coordination. The purpose of this study was to develop a scale, the Pelvic Floor Muscle Coordination Scale (PFMCS), to visually quantify pelvic floor muscle coordination during a physical therapy examination and to establish its inter-rater reliability and criterion-related validity. Number of Subjects: 20 women with varying levels of perceived pelvic floor dysfunction. Materials/Methods: Subjects completed the 20-item Pelvic Floor Distress Inventory short form (PFDI-20), which served as our criterion standard. Five investigators administered the PFMCS with standardized verbal cueing preceding performance of five activities. Five items were assessed: Respiration, Pelvic Floor Muscle Contraction, Extra-Pelvic Muscle Activity, Pelvic Floor Muscle Expansion, and Cough. Performance on each item was quantified using an ordinal scale ranging from 0-2 with a rating of 0 indicating optimal performance, a rating of 1 indicating dysfunctional performance, and a rating of 2 indicating absence of performance. Intraclass correlation coefficients (ICCs) were used to examine interrater reliability. Quadratic regression analyses were used to assess validity. Results: The PFMCS total score ICC was 0.792 and the pelvic floor muscle contraction and expansion subscales demonstrated good reliability, with ICC's of 0.812 and 0.798, respectively. Moderate reliability was found for quantifying the extra-pelvic muscle activity (ICC = 0.564), respiration (ICC = 0.603), and cough items (ICC = 0.642). Scores on the PFMCS were correlated with the pelvic organ prolapse distress (R2 = 0.355, p = 0.024) and the urinary distress (R2 = 0.304, p = 0.046) subscales of the PFDI-20. Conclusions: The PFMCS holds promise as an instrument that may facilitate a clinician's ability to objectively document observable patterns of pelvic floor muscle coordination. Total score inter-rater reliability of the scale was strong, as were the pelvic floor muscle contraction and pelvic floor muscle expansion subscales. Additionally, scores on the PFMCS were associated with the POPDI-6 and UDI-6 subscales of the PFDI-20 questionnaire as a criterion standard, indicating the observational scale has some level of criterion-related validity. Clinical Relevance: The PFMCS is a promising observational scale for pelvic floor coordination assessment. The scale demonstrated good reliability and scores were correlated with two subscales of the PFDI-20 questionnaire.