This study examined the Casey Foster Applicant Inventory-Applicant-Co-Parenting Scale (CFAI-CP), a new scale developed to measure foster parent applicants' co-parenting potential. Also, this study illustrates statistical methods used to analyze the psychometric properties of dyadic data. Factor structure and measurement invariance were tested with 111 approved foster couples. Mplus was used to accommodate ordinal-level data. Exploratory factor analysis supported a 10-item, unidimensional measure with excellent internal consistency reliability (.88 fathers,.89 mothers). Confirmatory factor analysis supported scalar measurement invariance but not structural invariance, as expected. Good construct validity was evident. Findings support the CFAI-CP as an empirically sound measure to assess foster parent co-parenting.