OBJECTIVE: To assess the diagnostic efficacy of 18F-FDG PET/MRI for lymph node (LN) metastasis primary staging in patients with colorectal cancer (CRC). METHODS: This study was conducted and reported in accordance with the PRISMA-DTA statement. Electronic databases (PubMed, Embase, Cochrane Library) were searched for studies on 18F-FDG PET/MRI for diagnosing LN metastasis. The pooled sensitivity (SEN), specificity (SPE), and area under the curve (AUC) were applied to assess the diagnostic performance. Heterogeneity was identified and processed using meta-regression and sensitivity analysis. All data analyses were performed via STATA 15 and Meta-Disc 1.4 software. RESULTS: There were finally 7 studies included, involving a total of 184 patients. The Spearman rank correlation coefficient was 0.108 (P = 0.818), with no threshold-effect observed. The pooled SEN was 0.81 (95%CI 0.66-0.90) and the SPE was 0.89 (95% CI 0.73-0.96). In sub-groups, prospective groups demonstrated to have the highest SEN of 0.92 (95%CI 0.79-1.00). The studies conducted by Catalano et al. and Kang et al. were considered to be potential sources of heterogeneity. CONCLUSION: 18F-FDG PET/MRI has shown remarkable diagnostic performance in identification of LN metastases in newly diagnosed CRC patients. It would be of great application value for the primary staging of CRC lymph node metastases.