Research suggests that toddlers with no language delay (NLD) should have better outcomes than those with language delay (LD). However, the predictive utility of language milestones relative to co-varying factors such as age at diagnosis, IQ, and ASD symptomatology is unclear. This study compared school-aged children with ASD and NLD (n = 59) to a well-matched group with ASD and LD (n = 59). The LD group was diagnosed at younger ages and their historical ASD symptoms were more severe than the NLD group. The groups were similar in current ASD symptoms and adaptive functioning at school age. Language milestones were correlated with adaptive functioning, but IQ and social symptoms of ASD were stronger predictors of functioning at school age. Therefore, language milestones may not be the best indicators of prognosis for children who are diagnosed after toddlerhood.