Introduction: Higher C-reactive protein (CRP) levels in critically ill patients are associated with increased disease severity and mortality rates. While branchedchain amino acids (BCAAs) have been extensively studied for their potential to enhance immunity in various diseases, research on the relationship between BCAAs and CRP levels in critically ill patients is scarce. This study aimed to assess the effect of BCAA supplementation on CRP levels in critically ill adult patients. Methods: An experimental randomised controlled trial was performed on 40 critically ill adults between December 2023 and May 2024. All subjects were randomly assigned to BCAA supplementation and control, with a 1:1 comparison. Subjects in the BCAA group were given 40 grams/day of BCAA (19 g/day leucine) supplementation with a leucine:isoleucine:valine ratio of 2:1:1.2 for ten days. No supplementation was given to the control group. CRP was measured from blood serum pre- and postintervention. Results: High CRP was found in all critically ill patients at baseline. Significantly lower CRP levels were found in the BCAA group compared to baseline (p=0.005) and control (p=0.001) post-intervention. Conclusion: High CRP was common in critically ill patients, and BCAA supplementation improved their CRP levels. This study implied that providing BCAAs for critically ill patients potentially improves their acute inflammation state. © (2025), (Malaysian Journal of Nutrition). All Rights Reserved.