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Emerging evidence associates vitamin D deficiency and vitamin D receptor (<i>VDR</i>) genetic variations with risk for breast cancer. This study investigated the prevalence of vitamin D deficiency and its association with tumor characteristics and the implications of <i>VDR</i> genetic variations for risk of breast cancer in Ethiopia. This unmatched case&#8315;control study involved 392 female breast cancer patients and 193 controls. The plasma 25-hydroxyvitamin D (25(OH)D₃) level was quantified in chemotherapy-na&#239;ve (<i>N</i> = 112) and tamoxifen-treated patients (<i>N</i> = 89). Genotyping for the <i>VDR</i> common variant alleles rs7975232 (<i>Apa</i>I), rs2228570 (<i>Fok</i>I), and rs731236 (<i>Taq</i>I) was done. Eighty-six percent of the patients were vitamin D deficient (&lt;50 nmol/L). Chemotherapy-na&#239;ve breast cancer patients had a higher prevalence of vitamin D deficiency (91.9% vs. 78.3%) compared to the tamoxifen-treated group (<i>p</i> &lt; 0.001). The prevalence of severe vitamin D deficiency (&lt;25 nmol/L) was significantly higher in chemotherapy-na&#239;ve (41.1%) than tamoxifen-treated (11.2%) patients. Vitamin D deficiency was not significantly associated with tumor characteristics or <i>VDR</i> genotype. The rs2228570 <i>GG</i> genotype was associated with increased risk of breast cancer (OR = 1.44, 95% confidence interval = 1.01&#8722;2.06). Our result indicates that rs2228570 might be a moderate risk factor for breast cancer development in the Ethiopian population. The high prevalence of severe vitamin D deficiency in treatment-na&#239;ve breast cancer patients indicates the need for nutritional supplementation of vitamin D at the time of chemotherapy initiation.