Abstract Objectives This study examines the psychometric properties of the Dutch adaptation of the Infant Caregiving Assessment Scales (INCAS). This standardized observation procedure is the first to assess both emotional and instrumental caregiving skills of mothers with a severe psychiatric disorder, during the postpartum period. Methods Mothers with and without a severe psychiatric disorder (N = 123) were observed at home at the infant age of 6 weeks during daily caregiving; changing a diaper, bathing, dressing, and feeding. Recordings of observations were coded independently by trained coders, blind for group membership. Subsequently, the component structure, internal consistency, interrater reliability, and concurrent validity of the INCAS were examined. Results Principal component analysis largely confirmed the two a priori defined caregiving domains. The internal consistencies of the emotional and instrumental domains were deemed excellent and good, respectively. The interrater reliability was substantial for the emotional domain and moderate for the instrumental domain. Furthermore, evidence for good concurrent validity of the emotional domain was found. Lastly, significant correlations were found between specific instrumental caregiving skills and maternal neuropsychological functioning. Conclusion Psychometric findings support the INCAS as a comprehensive and reliable instrument for standardized assessment of caregiving by mothers with a severe psychiatric disorder.