Background Acute anorectal abscess and fistula are common conditions that usually presents as a painful lump close to the anal margin. Tumors in the distal rectum and in the perianal region may mimic the symptoms and signs of anorectal sepsis, thereby leading to a delay in diagnosis and management. The purpose of this study was to describe patients presenting with acute perianal abscess or fistula who were subsequently diagnosed with anorectal cancer. Methods We performed a retrospective, review of all cases presenting with acute perianal abscess or fistula who were subsequently found to have anorectal carcinoma on biopsy in two tertiary centers. We analyzed the data focusing on the clinical features, laboratory values, clinical staging of the tumors, the subsequent management, the pathological staging, and the outcome of each patient. Results Overall, 3219 patients presenting with anorectal abscess or fistula were reviewed. Cancer was diagnosed in 16 (.5%) patients, 12 with adenocarcinoma of the rectum and 4 with squamous cell carcinoma of the anus. In 5 patients (31.2%), cancer was diagnosed in the setting of chronic perianal fistula, 4 of them had Crohn’s disease. In 10 patients (62.5%), cancer was not diagnosed during the initial evaluation of the acute symptoms. Conclusions A high index of suspicion is required to make the diagnosis of perianal tumors when assessing patients presenting with perianal sepsis, particularly those with Crohn’s disease, a long history of persistent perianal disease, and an advanced age. In most cases, proper drainage followed by proximal diversion are the surgical treatment of choice in the acute setting.