Voriconazole (VRCZ) is commonly administered to treat fungal infections in patients with hematological malignancies. Some of these patients experience VRCZ-associated visual hallucinations. We conducted a retrospective survey to investigate the characteristic features of this side effect. Patients with hematological malignancies who were treated with VRCZ for a fungal infection after hospitalization at Ichinomiya municipal hospital between 1 October 2005 and 31 December 2015 were included in this study (n = 103). Fifteen of these (14.6%) reported visual hallucinations that started on day 1-7. Seven of these 15 patients developed this symptom rapidly (day 1 or 2). Three patients had transient symptoms (lasting 2-12 days), 6 patients experienced hallucinations throughout the treatment, and the duration was unknown in 6 patients. Eleven patients experienced visual hallucinations when their eyes were closed (73 %) and these disappeared when they opened their eyes. One patient had visual hallucinations with open eyes, while the state of the eyes was unknown in 3 patients. The patients saw a range of images including people, animals, landscapes, and foods; several reported seeing images like those found in movies. In addition, 9 of 15 patients (60%) with visual hallucinations had visual disturbances. This was a higher proportion than that observed in patients who did not develop hallucinations (17 of 88; 19.3 %; P < 0.05). However, we found no significant difference between the blood VCRZ concentrations of patients who developed or did not develop visual hallucinations. This study indicated that most of these patients had visual hallucinations that manifested on eye closure, and they did not progress to serious mental illness. Our findings emphasized the importance of fully explaining the features of this symptom to each patient prior to starting VRCZ administration in order to reduce anxiety. In addition, since VRCZ discontinuation will compromise patient management, therapeutic drug monitoring should be used to increase the likelihood of successful therapy.