AbstractAimTo investigate if there is any benefit of adding clomiphene citrate (CC) + letrozole to controlled ovarian stimulation (COS) cycles on the total gonadotropin dose in POSEIDON group 4 diminished ovarian reserve (DOR) patients.MethodsA total of 61 DOR patients who underwent 150 COS cycles between 2020 and 2023 in our center were investigated retrospectively. The patients were divided into three main subgroups: group A, group B, and group C. In group A, gonadotropin stimulation started after the completion of 5 days of co‐treatment with CC (50 mg twice daily) and letrozole (2.5 mg twice daily). In group B, patients received gonadotropins after completing 5 days of letrozole (2.5 mg twice, daily), and in group C, patients started gonadotropins only.ResultsMean age was higher in groups A and B. Body mass index, previous parity, and mean AMH levels were similar between the groups. Day 2 antral follicle count was significantly lower in group A (0.90, 1.45 and 1.53; p = 0.017). The need for gonadotropins was lower in group A compared to groups B and C (p = 0.131, and p = 0.029; respectively). Cycle cancellation rates, follicle count on trigger day, number of mature oocytes, number of cleavage stage embryos, and number of blastocyst stage embryos were similar between the groups.ConclusionCC + letrozole co‐treatment before starting gonadotropin stimulation in POSEIDON group 4 DOR patients might reduce the need for gonadotropins, with similar live birth rates in COS cycles.