Purpose: Carpal Tunnel Decompression is an effective treatment for Carpal Tunnel Syndrome (CTS), however post-operative recovery varies between patients. Although objective preoperative tools have been investigated as predictors of recovery, findings remain inconsistent. This systematic review aims to investigate current literature to establish what is known about the relationship between objective pre-clinical assessments and post-operative recovery in patients with idiopathic CTS. Methodology: A systematic review was conducted in accordance with the PRISMA 2020 guidelines. MEDLINE, Embase, Scopus, CENTRAL, CINAHL and Web of Science were searched from database inception to 23rd of March 2026. Eligible studies included adults with idiopathic CTS undergoing open or endoscopic decompression, where objective preoperative tools were used to stratify severity, and postoperative recovery outcomes were reported with a minimum follow-up of three months. Study selection, data extraction, and critical appraisal were performed independently by two reviewers, and a third reviewer was used to resolve conflicts. Results: Our review included 17 studies published between 1997 and 2024. Nerve conduction studies (NCS) were the most investigated modality, followed by ultrasound, electromyography, and carpal tunnel pressure measurement. Eleven studies reported an association between preoperative severity and postoperative recovery, while six found no prognostic value. Where prognostic value was present, greater severity was generally associated with slower or incomplete recovery. Interestingly, although non-NCS modalities showed positive prognostic associations, they were underrepresented in the literature. Conclusion: Current evidence inconsistently supports a reliable objective preoperative prognostic tool for predicting recovery after carpal tunnel decompression. Further prospective and multimodal studies are needed to improve prognostic accuracy and counsel patients.