Many of the pesticides, as well as having synthetic content, are obtained from various plants moreover there are also organic based pesticides. One of them is Neem, Azadirachta indica, which is a wellknown plant with insecticidal properties and high biological activity levels. Azadirachtin (AZA) is a triterpenoid active compound that exists in the neem plant and its antiviral, antibacterial and antifungal properties have long been known. It can also be utilized commercially from azadirachtin. NeemAzal T/S is a commercial form in the European Union. It has been approved as a pesticide in organic farming and it contains 1% Azadirachtin. This and similar pesticide derivatives, when they are being mixed with the aquatic environment, have had a destructive influence on the aquatic ecosystem directly and on the people indirectly. That's why in our study we have studied AZA that is used as antibacterial in fish farming and have investigated the impact on the carp (Cyprinus Carpio, 1758 L.) using different doses (0, 1.2 and 2.4 ppm AZA) and times (4 and 30 days) and the levels of serum growth hormone (GH) and insulin-Like Growth Factor (IGF-1). In this study, the control group (based on 0 ppm), in the other dose groups in serum levels GH and IGF-1 a statistically significant reduction has occurred (p< 0.05). In the comparison depending on the period, in serum GH levels we have not observed statistically significant differences in acute and chronic (4 and 30 days, respectively)(p> 0.05), and in serum IGF-1 levels in 1.2 and 2.4 ppm dose groups the difference between periods has been significant (p< 0.05). At the end of the study, it has been determined that the chemicals which are used against fish parasites particularly in fish farming have negative effects on the growth of fish.