We report the case of a 70-year-old woman diagnosed with neural epidermal growth factor-like 1 antigen-positive membranous nephropathy and nephrotic syndrome. Following thorough exclusion of autoimmune diseases, medications, or infections as potential causes, colonoscopy was performed as part of malignancy evaluation, revealing an 18 mm villous adenoma in the sigmoid colon and a 7 mm tubulovillous adenoma in the cecum. Despite the absence of gastrointestinal symptoms initially and the absence of high-grade dysplasia in the pathology report, the patient experienced a remarkable improvement in symptoms and a reduction in nephrotic-range proteinuria following polypectomy, observed within a few months.