This study investigated the psychometrics of a recently developed global rating measure of videotaped parent-infant interaction, the Manchester Assessment of Caregiver–Infant Interaction (MACI), in a normative sample. Inter-rater reliability, stability over time, and convergent and discriminant validity were tested. Six-minute play interactions were blind-rated by trained coders in 147 healthy mother-infant dyads at 3–10 months postpartum using the MACI; 51% were re-assessed 4 or 7 months later. Infant cognitive functioning, language and temperament, parent-reported infant warmth and invasion, parental mood, and the parent’s own recalled experiences of being parented were measured. We report the internal psychometrics of the MACI, evidence of stability as predicted, and inter-rater reliability. MACI caregiver sensitive responsiveness showed convergent validity with parental state of mind (mood at 3–4 months; report of own childhood care and overprotection), while MACI infant affect (but not the caregiver scales) was associated with parent-rated infant warmth. All MACI scales showed discriminant validity with concurrent cognitive and language developmental status, and most temperament dimensions. In conclusion, the MACI demonstrates utility, reliability and preliminary validity data in a normative sample, which complements previous work using the MACI. Follow-up is needed to test predictive validity. The findings inform further improvements to the tool, and may guide those looking for a relatively brief way to examine the global qualities of parent, infant and dyadic interaction.