PURPOSE The pilot-phase report of the Joven & Fuerte prospective cohort broadly characterizes and assesses the needs of Mexican young women with breast cancer (YWBC). PATIENTS AND METHODS Women age ≤ 40 years with nonmetastatic primary breast cancer were consecutively accrued from 2 hospitals. Data were collected at the first/baseline oncology visit and 2 years later using a sociodemographic survey, European Organisation for Research and Treatment of Cancer Quality-of-Life (QOL) Questionnaire Core 30 (QLQ-C30) and Breast Cancer–Specific QOL Questionnaire (QLQ-BR23), Hospital Anxiety and Depression Scale (HADS), Female Sexual Functioning Index (FSFI), Sexual Satisfaction Inventory, and patients’ medical records. Pearson χ² and 2-sided t tests were used for statistical analysis. An unadjusted P value < .05 was considered significant. RESULTS Ninety patients were included, all with government health care coverage. Most had low monthly household incomes (98%) and at least a high school education (59%). There was a considerable prevalence of unpartnered patients (36%) and unmet parity (25%). Patients’ most common initial symptom was a palpable mass (84%), and they were most frequently diagnosed with stage III disease (48%), with 51% having had a physician visit ≤ 3 months since detection but 39% receiving diagnosis > 12 months later. At baseline, 66% of patients were overweight/obese, and this proportion had significantly increased by 2 years ( P < .001). Compared with baseline, global QLQ-C30 had improved significantly by 2 years ( P = .004), as had HADS-Anxiety ( P < .001). However, both at baseline and at 2 years, nearly half of patients exhibited FSFI sexual dysfunction. CONCLUSION These preliminary findings demonstrate that YWBC in Mexico have particular sociodemographic and clinicopathologic characteristics, reinforcing the necessity to further describe and explore the needs of these young patients, because they may better represent the understudied and economically vulnerable population of YWBC in limited-resource settings.