Background The infuence of healthcare system factors on treatment pathways for breast cancer has been studied extensively in lower-middle-income countries (LMICs), but in upper-middle-income countries (UMICs), this area is understudied. This article focuses on the experiences of breast cancer patients in Türkiye, a UMIC with a universal healthcare system. It explores variations in treatment pathways based on the type of health insurance provider (private or state). Methods The study uses an exploratory qualitative method based on in-depth interviews with 12 breast cancer patients. The inclusion criteria were Turkish nationality, female gender, and having received treatment from a private hospital within one year of the interview. A purposeful sampling strategy was employed to recruit patients who had either social health insurance only or who had private health insurance in addition to their social health insurance. A two-stage thematic analysis of the interview data was conducted. First, we examined whether the type of insurance provider makes a diference in treatment pathways; we then identifed healthcare system factors that explain these diferences. Results The study revealed two distinct pathways to treatment. These difer in terms of fnancial protection, service coverage, and patients’ sense of equity. Patients with private insurance reported easy access to timely and comprehensive treatment. Those without, however, had to navigate complicated routes to treatment; they generally had to resort to seeking treatment from more than one hospital. We found two healthcare system factors that explained the diferences: a failure to fully enforce the mandates of the state’s social health insurance in the private hospital sector and growing reliance on private insurance to gain access to essential services. Conclusions Based on data from the Turkish case, we conclude that healthcare system factors are indeed infuential in shaping treatment pathways for breast cancer in UMICs with universal healthcare. These factors include a failure to fully enforce the mandates of the state’s social health insurance programme in the private hospital sector and a growing reliance on private insurance to gain access to essential services. We note that this contrasts dramatically with the situation in LMICs, where the main factors are low-quality care and shortages of medical staf, medicines, and technologies.