Cognitive insight, defined as the ability to evaluate and correct one's own distorted beliefs and misinterpretations, is hypothesized to contribute to the development of psychotic symptoms. We investigated cognitive insight in individuals with at-risk mental state (ARMS), which is associated with a clinically high risk of psychosis. Sixty individuals with ARMS were compared with 200 healthy controls in terms of cognitive insight measured using the Beck Cognitive Insight Scale. We also investigated the relationship between cognitive insight and attenuated delusional symptoms. In addition, we examined differences in the cognitive insight of individuals with ARMS with or without near-threshold delusional symptoms and differences in the cognitive insight of individuals with ARMS with or without later transition to psychosis. The results showed that individuals with ARMS exhibited higher self-certainty than healthy controls, indicating impairments in cognitive insight in the former. More importantly, our results revealed that self-certainty was correlated with attenuated delusional symptoms and that individuals with ARMS who had near threshold delusional symptoms had higher self-certainty. These findings indicate that overconfidence in one's own beliefs or judgments might be related to the formation and maintenance of attenuated delusions in individuals with ARMS. (C) 2014 Elsevier Ireland Ltd. All rights reserved.