The purpose of this study was to study psychopathological and temperamental correlates of selective mutism (SM) (symptoms) in a mixed sample of non-clinical (n = 127) and clinically referred (n = 42, of whom 25 displayed the selective non-speaking behavior that is prototypical for SM) 6- to 12-year-old children. Parents completed questionnaires to measure their child’s symptom levels of selective mutism, social anxiety, autism spectrum disorder, and the temperament trait of behavioral inhibition. The results first and foremost showed that SM symptoms were clearly linked to social anxiety and an anxiety-prone temperament (behavioral inhibition), but findings also suggested that autism spectrum problems are involved in the selective non-speaking behavior of children. While the latter result should be interpreted with caution given the methodological shortcomings of this study, findings align well with the notion that SM is a heterogeneous psychiatric condition and that clinical assessment and treatment need to take this diversity into account.