Background: Sensory irregularities are commonly seen across developmental and intellectual disability groups. Identifying patterns of dysfunction within these clinical groups facilitates the development of appropriate intervention strategies. Thus, we evaluated the psychometric properties of the new Sensory Processing (SP) Scale Inventory rating scale. Method: Parents of children 4-18 years with and without sensory challenges completed the SP Scale Inventory. Item, domain, and subscale analyses were conducted to evaluate internal reliability, discriminant validity, and construct validity of the scale. Results: Items with adequate reliability and discriminant validity, a high frequency of endorsement by the clinical sample, and clear factor representation were retained. Reduced subscales demonstrated strong reliability and validity. Factor analysis verified the previously proposed sensory modulation subtypes. Conclusions: The new SP Scale Inventory appears to be a clinically useful parent rating scale to characterise patterns of sensory modulation in children with an intellectual or developmental disability.