This study investigated the relationship between serum vitamin D levels and cardiovascular disease risk factors in Type 2 Diabetes Mellitus (T2DM) patients attending the University of Maiduguri Teaching Hospital, Maiduguri, Borno State, Nigeria. A hospital-based cross-sectional design was employed, enrolling 70 confirmed T2DM patients and 70 age-matched control participants. Biochemical assessment included serum 25-hydroxyvitamin D [25(OH)D] by ELISA, fasting plasma glucose (FPG) by glucose oxidase method, glycated haemoglobin (HbA1c) by chromatographic method, full lipid profile, and albumin-adjusted calcium. Statistical analyses comprised independent samples t-test, Pearson correlation, logistic regression, and multiple linear regression. T2DM patients had markedly lower mean vitamin D levels (19.8±9.2 vs 26.4±10.1 ng/mL, p<0.001), with deficiency (<20 ng/mL) prevalent in 62.9% versus 31.4% of controls. Vitamin D deficiency conferred 2.68-fold higher odds of T2DM after full adjustment (95% CI: 1.08–6.65, p=0.033). Among T2DM patients, significant inverse correlations were established between vitamin D and FPG (r = −0.396, p<0.001), HbA1c (r = −0.361, p=0.002), BMI (r = −0.324, p=0.006), total cholesterol (r = −0.301, p=0.011), LDL-C (r = −0.284, p=0.016), and triglycerides (r = −0.257, p=0.032), while positive correlations were found with HDL-C (r = 0.245, p=0.041) and albumin-adjusted calcium (r = 0.312, p=0.008); none of these correlations were significant in controls. These findings demonstrate that vitamin D deficiency is significantly and independently associated with adverse cardiovascular risk factor profiles in T2DM patients, supporting routine vitamin D screening in this population and highlighting the need for further longitudinal and interventional research.