Background: For women with unilateral breast cancer, a surgical option is the removal of the cancer-free breast (contralateral prophylactic mastectomy, CPM). CPM among women with unilateral breast cancer is increasing despite the lack of evidence that it improves overall survival. There are limited data regarding factors associated with the decision to have CPM which limits the development of interventions to support informed decision-making. Methods: We recruited 343 women with newly diagnosed non-hereditary breast cancer prior to their first surgical consultation between 2012 and 2015. Women completed questionnaires assessing knowledge and level of interest in different surgical procedures including CPM, individuals with whom they discussed CPM and psychosocial factors. Results: The mean age of the participants was 56 years (range 25-82) and 48 women (14%) had CPM. Women were 57% white, 17% African American, 16% Hispanic, 10% other races. In univariate analyses, discussion of CPM with the medical oncologist (p = 0.03) and a strong interest in having mastectomy for the primary breast cancer (p < 0.001) were associated with CPM but discussion with the primary care provider (p = 0.63), spouses (p = 0.62) or breast cancer survivors (p = 0.45) was not associated with CPM. Women who had more breast cancer worry (p < 0.001), more intrusive thoughts about recurrence (p = 0.05), and more distress about body image (p = 0.003) were more likely to have CPM. In multivariable analysis, age (OR [odds ratio] 0.95, 95% CI [confidence interval] 0.91-0.99, p = 0.036 for every year increase in age), strong versus low interest in having mastectomy for the primary breast cancer (OR 12.16, 95% CI 1.53 -96.4, p = 0.02) and breast cancer worry (OR 1.17, 95% CI 1.10-1.36, p = 0.03 for every unit increase) remained significantly associated with CPM. Conclusions: Because of the important role that medical oncologists play in the decision making process of CPM, education regarding CPM should be focused on these providers in addition to surgeons. Addressing cancer worry among breast cancer patients is an area for intervention with decision support tools and counseling to ensure only patients most likely to derive clinical or psychosocial benefits will receive CPM.