To determine if random start ovarian stimulation in cancer patients provides similar results compared to conventional stimulation starting in follicular phase. Retrospective data analysis at a single center (CEGYR). All patients undergoing oocyte cryopreservation for fertility preservation due to recent cancer diagnosis were rewied from 2012 to 2018. Patients were grouped according to random start or conventional start of the ovarian stimulation. Conventional start was defined as scheduled in early follicular phase initiation of gonadotrophins; random start was initiated at any other moment of the menstrual cycle. The analyzed variables were: number of oocytes, number of matured oocytes (metaphase II), and cycle length. 71 cycles met inclusion criteria. Oocytes were collected of 23 (33%) patients on the random start group and 48 (67%) from the conventional one. Mean age was 33.8 years old in the conventional and 33.25 years old in the random start groups. (p:0.65 IC95%, 2.04-3.23). The mean number of oocytes collected were similar 11.9 (conventional) versus 10.4 (random) (p:0.47 IC95%, 2.65-5.66) and mean number of mature oocytes vitrified was also similar (metaphase II): 9.30 (conventional) vs 7.6 (random) (p:0.34 IC95%, 1.81-5.13). The cycle duration was different, being the conventional shorter (9.7 days) than the random group (11.3 days) (p:0.0019 IC95%, 0.61-2.58). Random start stimulation cycles for cancer patients has comparable results and allows patients to start gonadotrophin stimulation irrespective of menstrual cycle phase, with no impairment of oocyte yield and only a small increase of cycle duration.