PURPOSE: This study assessed lymphocyte-to-monocyte ratio (LMR) changes to predict postoperative recurrence in Fusobacterium nucleatum-positive (Fn-positive) CRC patients. PATIENTS AND METHODS: Clinical information and paraffin tissue specimens were collected from a retrospective cohort of 332 patients. The abundance of Fn in tumor tissue was measured using a quantitative polymerase chain reaction. We evaluated the prognostic value and diagnostic performance of the dynamic changes of LMR from pre-operative to post-treatment (pr-LMR-po) and the dynamic alterations of LMR from pre-operative to post-treatment to pre-end of follow-up (pr-LMR-f) in predicting recurrence in Fn-positive CRC. RESULTS: In the total cohort and adjuvant therapy group cohort, pr-LMR-po independently predicted recurrence-free survival in Fn-positive CRC patients. In the adjuvant therapy group, pr-LMR-po (High-High vs Low-Low: HR: 3.896, 95% CI: 1.503-10.095, p=0.005) was particularly significant. Meanwhile, pr-LMR-f can serve as a predictive biomarker for Fn-positive CRC recurrence, especially in the adjuvant therapy group cohort where the c-statistic for pr-LMR-f was 0.825 (95% CI: 0.804-0.8251), with a sensitivity of 83.6% and a specificity of 79.3%. Compared to the overall adjuvant therapy group cohort, the prognostic performance of pr-LMR-f was superior in the Fn-positive CRC adjuvant therapy group cohort (AUC: 0.825 VS 0.711). Finally, we constructed a prediction model combining pr-LMR-f and CEA. After internal validation using the bootstrap resampling, the model had an AUC of 0.9295, a sensitivity of 94%, and a specificity of 72.7% in the Fn-positive CRC adjuvant therapy group cohort. CONCLUSION: This study found that pr-LMR-po predicts Fn-positive CRC prognosis, and pr-LMR-f may predict Fn-positive CRC recurrence.