Background: Despite the risk of treatment-related infertility, implementation of fertility-preservation (FP) strategies among young patients with breast cancer is often suboptimal in resource-constrained settings such as Mexico. The “Joven & Fuerte: Program for Young Women With Breast Cancer” strives to enhance patient access to supportive care services, including FP measures through alliances with assisted-reproduction units and procurement of coverage of some of these strategies. This study describes patients from Joven & Fuerte who have preserved fertility, and assesses which characteristics were associated with the likelihood of undergoing FP. Methods: Women aged ≤40 years with recently diagnosed breast cancer were prospectively accrued. Sociodemographic and clinicopathologic data were collected from patient-reported and provider-recorded information at diagnosis and 1-year follow-up. Descriptive statistics, chi-square test, and simple logistic regression were used to compare patients who preserved fertility with those who did not. Results: In total, 447 patients were included, among which 53 (12%) preserved fertility, representing 38% of the 140 women who desired future biologic children. Oocyte/embryo cryopreservation was the most frequently used method for FP (59%), followed by temporary ovarian suppression with gonadotropin-releasing hormone agonists (GnRHa) during chemotherapy (26%), and use of both GnRHa and oocyte/embryo cryopreservation (15%). Younger age, higher educational level, being employed, having private healthcare insurance, and having one or no children were associated with a significantly higher likelihood of preserving fertility. Conclusions: By facilitating referral and seeking funds and special discounts for underserved patients, supportive care programs for young women with breast cancer can play a crucial role on enhancing access to oncofertility services that would otherwise be prohibitive because of their high costs, particularly in resource-constrained settings. For these efforts to be successful and widely applied in the long term, sustained and extended governmental coverage of FP options for this young group is warranted.