Simple SummaryWe conducted a systematic review and meta-analysis to investigate the relationship between pre-operative vitamin D (VD) levels and time-to-outcome in stage III colorectal cancer (CRC) patients. Four articles were included in the analysis, with pooled data from 2628 patients for overall survival and 2024 patients for disease-free survival. The results showed that patients with lower levels of VD had a 38% and 13% increased risk of death and recurrence, respectively, according to random-effects models. These findings suggest that a low VD concentration negatively impacts the time-to-outcome in stage III CRC.AbstractBackground: Vitamin D (VD) has been implicated in several diseases, including colorectal cancer (CRC). This study aimed to determine whether there is an association between VD levels and time-to-outcome in stage III CRC patients through a systematic review and meta-analysis. Methods: The study adhered to the PRISMA 2020 statement. Articles were searched in PubMed/MEDLINE and Scopus/ELSEVIER. Four articles were selected, with the primary objective of providing a pooled estimate of the risk of death specifically in stage III CRC patients based on pre-operative VD levels. Study heterogeneity and publication bias were analyzed using Tau2statistics and funnel plots. Results: The selected studies showed significant heterogeneity regarding time-to-outcome, technical assessments, and serum VD concentration measures. The pooled analysis of 2628 and 2024 patients revealed a 38% and 13% increase in the risk of death (HR: 1.38, 95% CI: 0.71–2.71) and recurrence (HR: 1.13; 95% CI: 0.84–1.53), respectively, for random-effects models among patients with lower levels of VD. Conclusions: Our findings suggest that a low concentration of VD has a significant negative impact on time-to-outcome in stage III CRC.