Background <p>Unicentric Castleman disease (UCD) is a rare group of non-neoplastic lymphoproliferative disorders. This study aims to summarize the specific ultrasonic manifestations of UCD.</p> Methods <p>This retrospective study included patients who underwent preoperative ultrasound for enlarged lymph nodes and were later diagnosed with UCD between January 2016 and March 2024. Ultrasound features, including lymph node size, cortical characteristics, corticomedullary interface, hyperechoic regions, and Doppler flow signals, were recorded. Pathological types were classified as hyaline vascular (HV), plasma cell (PC), or mixed. The ultrasonic features of each UCD subtype were systematically analyzed.</p> Results <p>A total of 41 patients were enrolled in the study, comprising 29 with HV-type, 4 with PC-type, and 8 with a mixed type. All patients presented with enlarged lymph nodes (LNs) characterized by a solitary mass, well-defined margins, and increased cortical thickness. Among these, 95.12% (39/41) exhibited an indistinct corticomedullary interface. Additionally, 41.46% (17/41) showed eccentric or asymmetrical cortical thickening, while 58.54% (24/41) demonstrated complete effacement of the fatty hilum. Approximately 24.39% (10/41) of cases exhibited macrocalcification, and 56.10% (23/41) displayed short linear hyperechoic foci within the lymph nodes. Furthermore, patients with HV-type and mixed-type conditions exhibited more abundant blood flow signals compared to those with PC-type (75.86% vs. 25% vs. 87.50%, <i>P</i> = 0.018).</p> Conclusions <p>Ultrasound characteristics of UCD generally comprise sizable, solitary masses with clearly delineated borders, a thickened cortex, and disappearance of the fatty hilum. Principal imaging indicators encompass microcalcifications and short linear hyper-echoes. Ultrasound represents an effective and non-invasive modality for the early identification and diagnosis of UCD.</p> Trial registration <p>Retrospectively registered.</p>