This study examined the convergent validity of the "Supports Intensity Scale-Adult Version" (SIS-A; Thompson et al., 2015a) and "Supports Intensity Scale-Children's Version" (SIS-C; Thompson et al., 2016a). Data from SISOnline (n = 129,864) for the SIS-A and from the SIS-C standardization sample (n = 4,015) were used for analyses. Using a pseudo multitrait-multimethod model, we estimated observed support needs scores as shared trait (support needs concept) and method (type, frequency, and daily support time) variances. Overall, trait variances more strongly influenced support needs scores than method variances, supporting the convergent validity of both versions of SIS. Findings also suggested that each of three methods of measuring support needs uniquely contributed to observed support needs ratings although different patterns existed between the SIS-A and SIS-C. [This paper was published in "American Journal on Intellectual and Developmental Disabilities" (EJ1119260).]