(1) Background: Over the past several years, there has been a renewed interest with regard to the effect of pre-operative vitamin D levels on post-surgical outcomes. Pre-operative vitamin D deficiency has been associated with many negative post-operative outcomes. However, the role of vitamin D in postoperative outcomes in colorectal liver metastasis (CRLM) resection is relatively uninvestigated. Our study investigated the correlation between preoperative vitamin D levels and postoperative complications in patients undergoing resection for CRLM. (2) Methods: We retrospectively examined the post-operative course of 109 patients, who were evaluated based upon preoperative vitamin D levels: the first group had vitamin D levels less than 25 nmol/L (VIT D < 25 nmol/L) (n = 12) vs. the second group who had vitamin D levels equal to or greater than 25 nmol/L (VIT D ≥ 25 nmol/L) (n = 97). (3) Results: Patients with lower pre-operative vitamin D levels (VIT D < 25 nmol/L) had significantly higher rates of blood transfusions (33.3% vs. 10.3%, p = 0.01), post-operative surgical complications (50% vs. 17.5%, p = 0.009), and infectious complications (25% vs. 7.2%, p = 0.04). However, there was no difference in overall survival seen between the two groups. (4) Conclusions: The results of our study indicate that patients with preoperative vitamin D deficiency (defined as preoperative vitamin D levels less than 25 nmol/L) may have an increased risk of postoperative complications in patients undergoing liver surgery for metastatic colorectal cancer.