Objective To evaluate the clinical value of pelvic computed tomography (CT) in the diagnosis of perianal abscess. Methods A retrospective study was conducted including patients with perianal abscess admitted to the Department of Proctology of our hospital between March 1, 2023 and June 30, 2023. All patients underwent preoperative pelvic CT or perianal ultrasonography. Intraoperative findings, including abscess type, location, and internal opening, were meticulously recorded. Surgical findings were used as the reference standard. The diagnostic performance of pelvic CT and perianal ultrasound was compared, and the clinical value of pelvic CT was analyzed. Results A total of 66 patients were enrolled, including 33 in the pelvic CT group and 33 in the perianal ultrasound group. Intraoperative findings revealed 37 cases (56%) of deep perianal abscess and 29 cases (44%) of superficial abscess. The most common abscess locations were left posterior (approximately 23%) and posterior midline (approximately 23%), followed by left anterior (approximately 20%), while other locations were less frequent. Most internal openings were located between the 3 o’clock and 6 o’clock positions (approximately 58%). The diagnostic accuracy of pelvic CT for abscess type was 100% (all deep and superficial abscesses were correctly identified), for abscess location was 93.94% (31/33), and for internal opening localization was 81.82% (27/33). The diagnostic accuracy of perianal ultrasound was 84.8% (28/33) for abscess type, 75.8% (25/33) for abscess location, and 72.7% (24/33) for internal opening localization. Pelvic CT demonstrated significantly higher accuracy than perianal ultrasound in distinguishing abscess type and exact location (P < 0.05). Although pelvic CT showed higher accuracy for internal opening detection, the difference was not statistically significant (P > 0.05). Conclusions Pelvic CT is a convenient, rapid, and accurate imaging modality for determining the type, location, and internal opening of perianal abscesses. Compared with other imaging techniques such as perianal ultrasonography and magnetic resonance imaging (MRI), pelvic CT offers significant advantages including non-invasiveness, shorter examination time, and lower cost. Pelvic CT has the potential to serve as a first-line preoperative imaging modality for perianal abscess. Further large-scale, multicenter, high-quality clinical studies are warranted to validate these findings and support its incorporation into future clinical guidelines.