Self-disturbances in schizophrenia have been explained and studied from the standpoint of an abnormal sense of agency (SoA). We devised an original agency attribution task that evaluated explicit experiences of temporal causal relation between an intentional action and an external event, without any confounding from sense of body ownership. We demonstrated that an excessive SoA was observed in patients with prominent positive symptoms including delusion and hallucination. Moreover, those patients had a greater tendency to feel SoA even when external events were programmed to precede their action (“backward causation”). Therefore, patients felt both forward and backward exaggerated causal efficacy during the intentional action (Maeda et al., Psychiatry Research2012). On the other hand, patients with predominant negative symptoms showed diminished SoA. Confusion in the experience of temporal causal relations between the self and the external world may underlie self-disturbances in schizophrenia. Aberrant SoA could be a fundamental vulnerability marker for schizophrenia.