Reliable and valid assessment of parenting and child behaviors is critical for clinicians and researchers alike, and observational measures of parenting behaviors are often considered the gold standard for assessing parenting and parent-child interaction quality. The current study sought to evaluate the reliability and validity of the Coder Impressions-Kindergarten (COIMP-K) measure. The current study was a secondary analysis of 274 parents and their children participating in a randomized control trial testing a brief parenting intervention for parents of children entering kindergarten. Families participated in baseline and follow-up assessments and videotaped observational tasks. Graduate and undergraduate coders completed the COIMP-K after achieving reliability. The aims of the current study were to assess the COIMP-K's (1) internal consistency using intercorrelations among COIMP-K subscales, (2) construct validity (3) convergent validity by comparing the COIMP-K subscales to parents' self-report of similar behaviors, (4) discriminant validity by comparing subscales to a parent-teacher communication measure as it is unrelated to parenting or child behaviors, and (5) congruence across time. Authors hypothesized the COIMP-K would demonstrate adequate internal consistency (Cortina, 1993), adequate construct, convergent, and discriminant validity, and to find congruence of the measure across time. Results demonstrated the factors had adequate internal consistency, construct, convergent, and discriminant validity, as well as longitudinal replicability and congruence over time. The study demonstrates that the COIMP-K is a reliable and valid tool for assessing observed family behaviors. [This paper was published in "Journal of Family Psychology."]