The primary objective of this study is to compare the oocyte yield in breast cancer patients undergoing controlled ovarian stimulation (COS) using letrozole and gonadotropins with patients undergoing COS with standard gonadotropins for elective cryopreservation of oocytes. Odds ratios (OR) for the number of mature oocytes were estimated. Pregnancy outcomes for breast cancer patients undergoing frozen-thawed 2-PN embryo transfers (FETs) after oncologic treatment were also noted. 220 and 451 cycles were identified in the breast cancer and the elective cryopreservation groups, respectively. Patients in the former group had lower peak estradiol levels [464.5 (315.5-673.8) pg/mL] compared to the latter [1696 (1058-2393) pg/mL; p < 0.01]. More oocytes were retrieved in the breast cancer group (12.3 ± 3.99) compared to the elective cryopreservation group (10.9 ± 3.86; p < 0.01). The odds for mature oocytes with letrozole and gonadotropins was 2.71 (95% CI 1.29-5.72; p = 0.01). Fifty-six FETs occurred in the breast cancer group. The clinical pregnancy and live birth rates per FET cycle were 39.7%, and 32.3%, respectively. Our findings suggest that COS with letrozole and gonadotropins yield more mature oocytes at lower estradiol levels compared to COS with gonadotropins alone. Breast cancer patients undergoing FET after oncologic treatment have live birth rates comparable to age-matched counterparts.