Event completion refers to the phenomenon in which the brain fills in missing information in cases where sensory information is causally implied. However, it remains unclear if people recognize that such information is internally generated and whether it is accurate enough for reliable judgment. Research on event perception often uses accuracy and confidence to assess humans’ perception. Yet, until now, there is no research investigating whether people have insight into the accuracy of their own judgments. As a first attempt to understand the confidence-accuracy relation in event perception, we analyzed existing data from an event completion study (Papenmeier et al., 2019) and replicated this experiment (N = 112). We used measures from Signal-Detection-Theory and calculated metacognitive efficiency, a bias-free indicator of the accuracy-confidence relation, for both experiments. Participants watched short soccer clips, followed by either a causal (e.g., seeing the ball flying) or non-causal sequence (e.g., cheering fans). They then decided whether they saw a critical ball contact, which was removed in half of the trials. They also rated their confidence in each decision. We hypothesized a lower detection accuracy and metacognitive efficiency in the causal than in the non-causal condition. Results showed a lower detection accuracy in the causal compared to the non-causal condition, implying that event completion occurs. However, the metacognitive efficiency comparison did not reveal any differences across the causality conditions, for both experiments. These findings suggest that causality affects detection accuracy but does not improve metacognitive insight, highlighting limits in evaluating one's own judgments.