Clinicians report primarily using functional behavioral assessment (FBA) methods that do not include functional analyses. However, studies examining the correspondence between functional analyses and other types of FBAs have produced inconsistent results. In addition, although functional analyses are considered the gold standard, their contribution toward successful treatment compared with other FBA methods remains unclear. This comparative effectiveness study, conducted with 57 young children with autism spectrum disorder, evaluated the results of FBAs that did (n = 26) and did not (n = 31) include a functional analysis. Results of FBAs with and without functional analyses showed modest correspondence. All participants who completed functional communication training achieved successful outcomes regardless of the type of FBA conducted.