DSM-5 classifies Selective Mutism (SM) among anxiety disorders, and a majority of children with SM comply with symptomatology of Social Anxiety Disorder (SAD). It is still discussed whether SM constitutes a discrete disorder entity or merely an extreme form of SAD. Past research that compared anxiety levels in both disorders resulted in conflicting conclusions, which might be due to the adoption of questionnaire measures or experimental designs that comprised in vivo situations. In vivo situations contain the possibility to avoid the feared situations for children with SM by remaining silent, which is not true for children with SAD. Participants aged eight to 18 years (M = 13.30 years, SD = 3.26) with above cut-off symptomatology in SM (n = 52), SAD (n = 18), and typical development (n = 41) participated in an online-based study. They evaluated 21 videos with neutral, embarrassing, or speech-demanding situations with respect to their anxiety elicitation. There was no general difference in anxiety levels between participants with elevated SM and SAD symptomatology, and both groups rated embarrassing situations similarly. However, only children with SM features experienced speech-demanding situations as anxiety eliciting, as embarrassing situations and more so than participants in both other groups. Results of the present study indicate that SM is an anxiety disorder with a specific anxiety pattern rather than an extreme form of SAD. In addition to typical social phobic situations, interventions for children with SM should also address situations involving speech demands.