Salinity stress is one of the important factors affecting all growth processes, from seed germination to seedling development, plant growth, yield and quality. In this study, the effects of serotonin treatments on the germination of pepper seeds (Capsicum annum L.) under salt stress were investigated. Different doses of salt (0, 75 and 150 mM NaCl) and serotonin (S0:0 µM, S1:5 µM, S2:10 µM, S3:15 µM, S4: 20 µM) were used. The applied seeds were placed between the papers in petri dishes, watered with the prepared salt solutions and left to germinate at 25 °C. In the study, parameters related to germination percentage, germination speed, mean germination time, daily mean germination time, peak value and germination value were investigated. As a result of the research, it was determined that the germination of pepper seeds decreased in parallel with increasing salt concentrations, and this negative effect of salt stress decreased with serotonin applications. Although it changes depending on the serotonin doses, it has been observed that significant effects occur on the measured germination parameters, and the best germination was observed at S1 and S2 doses. It is thought that the application of serotonin will have positive effects on the germination of pepper seeds under salt stress, and these effects may also occur during the plant growth period.