Aim The purpose of this study was to establish the validity, reliability, stability and sensitivity to change of the family‐centred Movement Assessment of Children (MAC) in typically developing infants/toddlers from 2 months (1 month 16 days) to 2 years (24 months 15 days) of age. Background Assessment of infant/toddler motor development is critical so that infants and toddlers who are at‐risk for developmental delay or whose functional motor development is delayed can be monitored and receive therapy to improve their developmental outcomes. Infants/toddlers are thought to be more responsive during the MAC assessment because parents and siblings participate and elicit responses. Methods Two hundred seventy six children and 405 assessments contributed to the establishment of age‐related parameters for typically developing infants and toddlers on the MAC. The MAC assesses three core domains of functional movement (head control, upper extremities and hands, pelvis and lower extremities), and generates a core total score. Four explanatory domains serve to alert examiners to factors that may impact atypical development (general observations, special senses, primitive reflexes/reactions, muscle tone). Construct validity of functional motor development was examined using the relationship between incremental increases in scores and increases in participants' ages. Subsamples were used to establish inter‐rater reliability, test–retest reliability, stability and sensitivity to change. Results Construct validity was established and inter‐rater reliability ICCs for the core items and core total ranged from 0.83 to 0.99. Percent agreement for the explanatory items ranged from 0.72 to 0.96. Stability within age grouping was consistent from baseline to 6 months post‐baseline, and sensitivity to change from baseline to 6 months was significant for all core items and the total score. Conclusion The MAC has proven to be a well‐constructed assessment of infant and toddler functional motor development. It is a family‐centred and efficient tool that can be used to assess and follow‐up of infants and toddlers from 2 months to 2 years.