Background: About my Child, 26-item version (AMC-26) was developed as a measure of child health ‘complexity’ and has been proposed as a tool for understanding the functional needs of children and the priorities of families. Methods: The current study investigated the reliability and validity of AMC-26 with a sample of caregivers of children with neurodevelopmental disorders (NDD; n = 258) who completed AMC-26 as part of a larger study on parenting children with NDD. A subsample of children from the larger study (n = 49) were assessed using standardized measures of cognitive and adaptive functioning. Results: Factor analysis revealed that a four-component model explained 51.12% of the variance. Cronbach’s alpha was calculated for each of the four factors and for the scale as a whole, and ranged from 0.75 to 0.85, suggesting a high level of internal consistency. Construct validity was tested through comparisons with the results of standardized measures of child functioning. Predicted relationships for factors one, two and three were statistically significant and in the expected directions. Predictions for factor four were partially supported. AMC-26 was also expected to serve as an indicator of caregiver distress. Drawing on a sample of caregivers from the larger study (n = 251) the model was found to be significant and explained 23% of the variance in caregiver depressive symptoms (R2 = .053, F (1, 249) = 14.06, P < .001). Conclusions: Based on these observations, the authors contend that AMC-26 may be used by clinicians and researchers as a tool to capture child function and child health complexity. Such a measure may help elucidate the relationships between child complexity and family well-being. This is an important avenue for further investigation.