BACKGROUND: Colovesical fistula (CVF) is a rare condition characterized by an abnormal connection between the colon and the urinary bladder. While diverticular disease is the most common cause, this report describes a unique case of CVF resulting from an ingested foreign body. CASE PRESENTATION: A 78-year-old woman with a history of COPD and chronic lymphocytic leukemia presented with prolonged urinary symptoms, including dysuria, frequency, hematuria, and a history of pneumaturia and fecaluria. A CT scan with rectal contrast revealed thickening of the sigmoid colon, contrast material extending into the bladder, and an associated air-fluid level. Cystography and colonoscopy confirmed the presence of a CVF with inflammation and narrowing of the sigmoid colon. Remarkably, the patient spontaneously passed a "bone-like" object through the urethra, later identified as a chicken bone. She underwent a single-stage resection of the affected sigmoid colon with primary anastomosis and bladder repair. Histopathology confirmed chronic inflammatory changes consistent with fistula formation. The patient recovered uneventfully. DISCUSSION: CVF most commonly arises from diverticulitis, but migration of ingested foreign bodies leading to erosion into the urinary system is rare. This case highlights the importance of considering foreign body ingestion in CVFs without an identifiable cause. CONCLUSION: Although rare, ingested foreign bodies-such as a chicken bone-can erode the bowel wall and cause a CVF. The spontaneous urethral passage of such objects is an even rarer event. This case underscores the importance of thorough history-taking and imaging studies to identify unusual causes of CVF.