Sleep-related problems are prevalent in patients with psychotic disorders, yet their contribution to fluctuations in delusional experiences is less clear. This study combined actigraphy and experience-sampling methodology (ESM) to capture the relation between sleep and next-day persecutory symptoms in patients with psychosis and prevailing delusions. Individuals with current persecutory delusions (PD; n = 67) and healthy controls (HC; n = 39) were assessed over 6 consecutive days. Objective sleep and circadian rhythm measures were assessed using actigraphy. Every morning upon awakening, subjective sleep quality was measured using ESM. Momentary assessments of affect and persecutory symptoms were gathered at 10 random time points each day using ESM. Robust linear mixed modeling was performed to assess the predictive value of sleep measures on affect and daytime persecutory symptoms. PD showed significantly lower scores for subjective quality of sleep but significantly higher actigraphic-measured sleep duration and efficiency compared with HC. Circadian rhythm disruption was associated with more pronounced severity of persecutory symptoms in HC. Low actigraphy-derived sleep efficiency was predictive of next-day persecutory symptoms in the combined sample. Negative affect was partly associated with sleep measures and persecutory symptoms. Our results imply an immediate relationship between disrupted sleep and persecutory symptoms in day-to-day life. They also emphasize the relevance of circadian rhythm disruption for persecutory symptoms. Therapeutic interventions that aim to reduce persecutory symptoms could benefit from including modules aimed at improving sleep efficacy, stabilizing sleep-wake patterns, and reducing negative affect. (PsycInfo Database Record (c) 2021 APA, all rights reserved).