The process of radicalization is often discussed and investigated without a clear outcome definition, as is the similar concept of extremism; moreover, research is usually conducted on adults, despite studies pointing to adolescence as the crucial time during which radicalization processes develop. Building upon previous literature, we propose three possible outcomes of the radicalization process: benevolent radicalism, malevolent radicalism, and extremism. To operationalize these outcomes, we develop a questionnaire measuring four constructs, namely political violence legitimization, political and religious (in-)tolerance, political system preference, and ingroup superiority beliefs. We developed an instrument specifically suitable for adolescents, using n = 1260 German-speaking adolescents (13-20 years) in item development and n = 622 in scale testing and validation. The resulting 61 items and five scales were developed and validated through a combination of item analysis, cognitive interviewing, exploratory and confirmatory factor analyses. Support was found for each of the five scales in terms of reliability, discriminant and concurrent validity. We therefore found the Adolescent Radicalization Outcomes Questionnaire to be a valid and reliable instrument.