<p>The Bilateral Water Sign (BWS) is an imaging finding that manifests following prolonged compression of the trigeminal nerve by offending vessels. The Bilateral Water Sign is considered to reflect the underlying neurovascular compression relationship. To investigate the relationship between the presence of BWS and the surgical outcomes of microvascular decompression for hemifacial spasm (HFS). Patients diagnosed with hemifacial spasm who met the inclusion criteria were subjected to imaging examinations and evaluations and were subsequently categorized into a BWS-negative group (n = 42) and a BWS-positive group (n = 45). The correlation between the presence of BWS and the outcomes of microvascular decompression was assessed based on postoperative symptom recovery and intraoperative lateral spread response (LSR) findings. Additionally, demographic characteristics were analyzed. Compared with the BWS-negative group (n = 42), the BWS-positive group (n = 45) demonstrated significantly higher short-term efficacy, with an effective remission rate of 97.8% versus 73.8% (P &lt; 0.001). In the BWS-negative group, long-term efficacy was significantly superior to short-term efficacy (85.7% vs. 73.8%, P &lt; 0.001). Furthermore, the intraoperative LSR disappearance rate was significantly higher in the BWS-positive group (n = 27) than in the BWS-negative group (P = 0.042). Patients with BWS identified by high-resolution magnetic resonance imaging demonstrated superior postoperative relief of muscle spasm symptoms. This imaging finding may serve as a valuable reference for preoperative assessment of surgical risks and benefits. Furthermore, patients exhibiting significant residual symptoms postoperatively and a negative preoperative BWS should be managed cautiously when considering reoperation or alternative therapeutic strategies.</p>