Background Postoperative insulin resistance (PIR) represents an important characteristic of metabolic response following surgical injury. Clinical outcomes are negatively correlated to postoperative insulin resistance and hyperglycemia, indicating a novel treatment for reducing postoperative insulin resistance is urgently needed. The current work aimed to assess the protective effects of branched-chain amino acids (BCAA) on glucose metabolism disorders induced surgically in a rat model, and to explore the underpinning mechanism. Methods and results Rats were randomly assigned to 2 groups, including the control and BCAA groups. Rats were given a compulsory oral 3 mL load by gavage two hours before surgery. The results showed that BCAA remarkably reduced glycemia by suppressing liver gluconeogenesis via reduction of cAMP-response element-binding protein-regulated transcription coactivator 2 (CRTC2) and glucose-6-phosphatase (G6PC) gene and protein expression levels (all Ps < 0.05). Conclusions This study revealed that BCAA lower blood glucose levels by reducing liver gluconeogenesis without significant elevation of plasma insulin levels. We anticipate that preoperative BCAA supplementation may be a means for preventing postoperative insulin resistance.