In this study, the effect of different doses of recombinant gonadotropin-releasing hormone (rGnRH) and ovaprim (OVP) was investigated on reproductive function, sex steroid levels, and stress response in female koi carp, Cyprinus carpio, females. For this purpose, female koi carps (980.66 ± 23.46 g) were divided into five experimental groups and injected with the following preparation procedure: 0.9% NaCl with 5 mg/kg body weight (BW) of domperidone (Dop) (Control, C), 0.5 ml/kg BW of ovaprim (OVP); 10 μg kg BW−1 of rGnRH with 5 mg/kg of Dop (rGn10), 25 μg/kg BW of rGnRH with 5 mg/kg of Dop (rGn25), and 50 μg/kg BW of rGnRH 5 with mg/kg of Dop (rGn50). To evaluate sex steroids and stress indicators in the females, blood samples were collected before injection and 6, 12, and 24 h post-injection. The results indicated that the females were significantly different in terms of the number of spawned females, with the highest numbers in OVP and rGn25 treatments and the lowest number in the control treatment. Significant differences were observed between hormone-treated fish at the latency period, and the highest latency was obtained in the rGn10 treatment compared to shorter latencies in the other treatments. Sex steroid levels 17β estradiol (E2), testosterone (T), and 17α, 20β-dihydroxy-4-pregnen-3-one (DHP) were affected by the hormonal treatments. Levels of E2 decreased in rGnRH and OVP treatments at 6 and 12 h after the injection. T and DHP levels increased in rGnRH and OVP treatments at 6 and 12 h after the injection and then decreased at 24 h post-injection. Cortisol levels increased at 6 and 12 h post-injection and decreased 24 h after the injection. No changes were observed in lactate and glucose levels at 6 h after the injection, but its levels were significantly higher in hormone-injected treatments than in the control treatment at 12 h after the injection. rGnRH could induce spawning, and the highest spawning rate and efficiency were measured in the rGn25 treatment. According to the results, rGnRH may be suggested as an alternative to other hormones used for artificial propagation in koi carp.