<p>Asenapine (ASE) is a second-generation antipsychotic with potential efficacy against insomnia due to its pharmacological profile. This study aimed to evaluate the effects of ASE add-on therapy on sleep in schizophrenia patients. Participants in this observational study comprised four schizophrenia patients with complaints of insomnia who planned to receive ASE as add-on therapy. ASE was added to the existing pharmacological regimens and administered according to the approved dosage and administration guidelines. Pre-existing treatments were continued throughout the 28-day observation period. Psychiatric symptoms were assessed using the Positive and Negative Syndrome Scale and subjective insomnia severity was assessed using the Insomnia Severity Index. Objective sleep parameters were evaluated using a portable sleep electroencephalogram device. Three of the four patients completed the 28-day observational period. In all three cases, ASE was effective for improving positive symptoms and subjective insomnia symptoms. However, no consistent trends in objective sleep parameters were observed. These preliminary findings suggest that ASE may be a viable adjunctive treatment option for patients with schizophrenia experiencing insomnia and positive symptoms. Further studies with larger, controlled samples are needed to validate these effects.</p>