Motivation has been studied extensively in physical activity (PA) research and nearly identical instruments have been utilized in physical education (PE) research. PE differs from PA because a distinct educational goal is the focus. Therefore, measures created for PA research may not account for the uniqueness of the PE context questioning the validity of the scores. One theory examined in PA research is perception of competence (POC), which implies that the more competent an individual feels the greater the desire to engage and persist in activity (Harter, 1978). The purpose of this study was to design and validate the scores for an instrument measuring POC in middle school PE. A multi-phase design was employed consisting of a theoretical review to identify factors reported as influencing POC in PE, an elicitation study to ascertain appropriate language of middle school students to increase readability, pre-pilot review by 11 PE specialists, a pilot study with middle school PE students (N = 352), a content validation by 34 pedagogy scholars, and a final validation study (N = 1281). Pilot study analysis included exploratory factor analysis (EFA) and examination of scree plots and factor loadings followed by confirmatory factor analysis (CFA). A 30 item survey was created addressing three factors utilizing a 5-point Likert-type scale. The resulting factors were personal, social (peer and family), and teacher. The content validity study resulted in 98% agreement in identifying item categories. The final validation study included middle school students representing seven schools in three states. Data analysis examining scores' construct validity in the validation study mirrored the pilot study including EFA, CFA, and examination of Cronbach's alpha coefficients. EFA refined the three initially identified factors to specify personal experience, peer, and teacher behaviors as factors impacting POC. From the analysis a three factor and two factor model were identified. The three factor model included personal experience, peer, and teacher behavior and represented an acceptable fit (Hu & Bentler, 1999) (GFI = .90, AGFI = .86, RMSR = .07, RMSEA = .09). The alpha coefficients were .66, .80, and .85 respectively. A two factor model excluding personal experience was explored in further analysis and reported excellent fit statistics (GFI = .98, AGFI = .97, RMSR = .03, RMSEA = .05). The results of this study suggest that an instrument employing a two or three factor model provides reliable and valid scores of POC measurement in middle school PE.