AimTo develop the Mini‐Manual Ability Classification System (Mini‐MACS) and to evaluate the extent to which its ratings are valid and reliable when children younger than 4 years are rated by their parents and therapists.MethodThe Mini‐MACS was created by making adjustments to the MACS. The development involved a pilot project, consensus discussions within an expert group, and the creation of a test version of the Mini‐MACS that was evaluated for content validity and interrater reliability. A convenience sample of 61 children with signs of cerebral palsy aged 12 to 51 months (mean age 30.2mo [SD 10.1]) were classified by one parent and two occupational therapists across a total of 64 assessments. Agreement between the parents' and therapists' ratings was evaluated using the intraclass correlation coefficient (ICC) and the percentage of agreement.ResultsThe first sentence of the five levels in the MACS was kept, but other descriptions within the Mini‐MACS were adjusted to be more relevant for the younger age group. The ICC between parents and therapists was 0.90 (95% confidence interval [CI] 0.79–0.92), and for the two therapists it was 0.97 (95% CI 0.78–0.92). Most parents and therapists found the descriptions in the Mini‐MACS suitable and easy to understand.InterpretationThe Mini‐MACS seems applicable for children from 1 to 4 years of age.