The lives of caregivers can be deeply impacted by having a child with a developmental disability (DD). To offset those impacts, caregivers may engage in accommodations, or strategies to bolster everyday functioning. The nature and extent of these accommodations can provide insight into how the family is doing and what supports are needed from a family-centered perspective. This paper presents the development and preliminary validation of the Accommodations & Impact Scale for Developmental Disabilities (AISDD). The AISDD is a rating scale that measures day-to-day accommodations and impacts of raising a child with a DD. A sample of 407 caregivers of youth with DDs (M[subscript age] = 11.7 years; 63% males) completed the AISDD, along with measures of caregiver strain, daily challenges, child adaptive behavior, and behavior and emotional regulation. The AISDD is a unidimensional, 19-item scale with excellent internal consistency (ordinal alpha = 0.93) and test-retest (ICC = 0.95) reliability. Scores were normally distributed and sensitive to age (r = - 0.19), diagnosis (ASD + ID > ASD > ID), adaptive functioning (r = - 0.35), and challenging behaviors (r = 0.57). Finally, the AISDD showed excellent convergent validity with similar measures of accommodations and impacts. These findings support the use of the AISDD as a valid and reliable tool for measuring accommodations among caregivers of individuals with DDs. This measure shows promise in its ability to identify which families may need additional support for their children.