Background: Immune checkpoint inhibitors have recently been widely used for advanced cancers and are known to cause ocular complications. We herein report a case developing bilateral serous retinal detachments, without ocular inflammation, after starting nivolumab treatment. Case presentation: A 73-year-old man was referred to our hospital, having become aware of metamorphopsia 2 months after starting nivolumab (anti-programmed cell death protein 1 monoclonal antibody) for malignant melanoma of the nasal cavity. The initial corrected visual acuity of the right eye was 20/20, and that of the left eye was 20/16. There were no inflammatory findings in the anterior segment or the vitreous. Vitelliform lesions were found in the macular area of both ocular fundi, consistent with serous retinal detachment and subretinal deposits. Swept source optical coherence tomography showed diffuse thickening of the outer photoreceptor segment and thickening of the choroid. Two months after the initial diagnosis, multiple vitelliform lesions were noted, and the fundus findings had worsened. Indocyanine green fluorescein angiography showed delayed inflow in the peripapillary and posterior pole regions in the early phase of imaging. Fundus autofluorescence showed hyperautofluorescence consistent with most of the vitelliform lesions on color fundus photography. Conclusions: Nivolumab may have impaired the pumping and phagocytosis functions of retinal pigment epithelial cells, resulting in bilateral serous retinal detachments and thickening of the photoreceptor outer segment. This is the first case report, to our knowledge, describing multiple bilateral serous retinal detachments and outer segment thickening without inflammation in a patient treated with nivolumab.