Background and aims: Internet video streaming (VS) has become a popular leisure activity among the majority of adolescents, especially under the COVID-19 pandemic. Research on binge watching patterns in adults suggests an addictive potential of VS. To date, no unified conceptualization on problematic VS and no standardized assessment tools for adolescents exist even though they might be especially vulnerable. Methods: STREDIS-A is based on the ICD-11 criteria of gaming disorder. It was validated in a representative sample of 959 dyads of 10- to 17-year old adolescents with frequent VS and a respective parent using standardized questionnaires on Internet addiction, depressive and anxiety symptoms, insomnia, loneliness, and academic performance in an online survey. Item structure was investigated by factorial analyses. Cutoffs were estimated and latent profile analysis was performed. Results: The two-factorial structure of STREDIS-A describes cognitive-behavioral symptoms and negative consequences of VS. Internal consistency and criterion validity were good to excellent. It could excellently discriminate between affected and non-affected adolescents. Discussion and conclusions: The present study makes a significant contribution to the conceptualization of a new phenomenon. It provides the very first tool to assess streaming disorder in adolescents for clinical and research settings. Clinical validation is highly warranted.  Kulcsszavak: problematic streaming, streaming disorder, ICD-11, adolescents, binge watching