OBJECTIVE: The psychometric properties of a newly developed, clinically-sensitive, observational measure of parenting behavior, the Parenting Clinical Observational System (P-COS), are presented. The P-COS expands on existing observational coding systems by integrating qualitative and quantitative aspects of parenting behavior to directly inform clinical decision-making with parents of young children with disruptive behaviors. DESIGN: Reliability and validity data were examined in a sample of mother-preschooler dyads ( = 335), and test-re-test reliability was assessed on an independent sample ( = 29). RESULTS: Evidence was found for the reliability and validity of the P-COS, including evidence of inter-rater reliability, internal consistency, and distinctness of the three theorized P-COS domains: Responsive Involvement, Constructive Discipline, and Problematic Discipline. Convergent and divergent validity data are presented as well. The P-COS demonstrated incremental validity in predicting child disruptive behavior over and above self-reported parenting and was associated with change in child clinical status over time. CONCLUSIONS: Clinically informative observation methods that assess multiple dimensions of parenting within the context of a child disruptive behavior assessment provide useful information for directing treatment efforts.