Abstract Tamoxifen and other endocrine agents have proven benefits for women with ductal carcinoma in situ (DCIS), but low patient acceptance is widely reported. We examined factors associated with tamoxifen acceptance and adherence among DCIS patients who received a recommendation for therapy in a multidisciplinary setting. Using our institutional database, we identified women diagnosed with DCIS, 1998 to 2009, who were offered tamoxifen. We recorded data on demographics, tumor and therapy variables, tamoxifen acceptance, and adherence to therapy for ≥4 years. Univariable and multivariable analyses were conducted using logistic regression to identify factors specific to each group that were related to acceptance and adherence. A total of 555 eligible women identified, of whom 369 were offered tamoxifen; 298 (81%) accepted, among whom 214 (72%) were adherent, 59 of 298 (20%) were nonadherent, and for 25 (8%), adherence was undetermined. After stepwise elimination in adjusted logistic regression models, acceptance of breast radiotherapy was associated with acceptance of tamoxifen [OR, 2.22; 95% confidence interval (CI), 1.26–3.90; P < 0.01], as was a medical oncology consultation (OR, 1.76; 95% CI, 0.99–3.15; P = 0.05). Insured patients were more likely to adhere to tamoxifen (OR, 6.03; 95% CI, 2.60–13.98; P < 0.01). The majority of nonadherent women (n = 38/56, 68%) discontinued the drug during the first year of treatment with 48 (86%) citing adverse effect(s) as the reason. In a multidisciplinary, tertiary care setting, we observed relatively high rates of acceptance and adherence of tamoxifen. Acceptance of tamoxifen and radiotherapy were associated, and adherence was influenced by insurance status. Key Message: Tamoxifen acceptance and adherence following resection of DCIS of the breast is related to acceptance of radiotherapy and may be improved by confirmation of the recommendation by a medical oncologist. Despite the low cost of tamoxifen, adherence to therapy is significantly impacted by lack of insurance; those who discontinue therapy report adverse effects as a major reason. Cancer Prev Res; 10(7); 389–97. ©2017 AACR.