OBJECTIVES: The present report examines the monitoring of self-generated speech in adolescents with 22q11.2 deletion syndrome (22q11DS), a neurogenetic disorder associated with very high risk for psychosis. DESIGN: Between-participant group design. METHODS: In this study, 20 adolescents with 22q11DS, 19 age- and IQ-matched controls, and 19 typically developing adolescents were enrolled. Participants completed a speech-monitoring task, in which they were asked to silently or overtly read a series of word and non-word items. Subjects then filled out a recognition sheet containing studied and novel items. They were asked to identify the previously studied item, and to attribute the reading condition (silent vs. overt) under which each recognized item was encoded. RESULTS: Adolescents with 22q11DS commit more external attribution errors compared to both control groups, by exhibiting an increased tendency to report silently read items as though they had been read overtly. Further, results suggest that increased cognitive effort exacerbates the external attribution tendency in adolescents with 22q11DS. Increased internal attributions were also observed in the IQcontrol and 22q11DS groups in comparison to typically developing adolescents. CONCLUSIONS: Similarly to adult individuals exhibiting positive symptoms of psychosis, adolescents with 22q11DS exhibit an external attribution bias for inner speech. This bias seems to be exacerbated by increased cognitive effort, suggesting a failure to recollect information pertaining to cognitive operations during self-monitoring. Cognitive biases associated to schizophrenia may be detected in adolescents at very high risk for psychosis. These observations provide further evidence for the presence of an external attribution bias along the clinical continuum of psychosis vulnerability.