Objective: To examine breast cancer patients’ reasons to seek a second opinion (SO) and the underlying variables. To find out more about the outcome of the SO, the perceived helpfulness and the effect on the physician-patient relationship. Methods: In 2017, 4626 newly diagnosed breast cancer patients from 86 hospitals in Germany completed a postoperative mail survey (response rate = 89.04%). Data from 419 SO-seeking patients was obtained and analyzed by conducting logistic regression and non-parametric group comparisons. Results: Reasons to seek an SO were mostly unrelated to the physician-patient relationship. Reasons related to the physician-patient-relationship were associated with a lower education level. The SO mostly (72.2%) equaled the first opinion. A different treatment plan recommendation (25%) reportedly affected the patients’ relationship with their primary physician. Patients who received a different diagnosis reported more fear of progression. Most patients found the SO helpful. Conclusion: The reasons to seek an SO are primarily unrelated to the physician-patient relationship. However, less educated patients seem to have different reasons to seek an SO. These reasons were reportedly associated with the physician-patient relationship. Practice implications: Physicians may need to explicitly ascertain the patient's needs within the physician-patient communication to avoid inequalities based on patient education.