The study was conducted out at the Ministry of Agriculture's Poultry Research Station/Animal ResourcesDepartment/Agricultural Research Center. To see how body weight (BW) and leptin hormone (LEP) levels inbreeder blood affect fertility and hatchability. 140 Iraqi local laying chickens (120 females + 20 males) aged 28weeks were used in the study. Following the numbering of The experiment was divided into three periods,each lasting 28 days, during which the breeder's live body weight was recorded and divided into two categories(greater than 1.5 kg and less than 1.5 kg), and blood samples were collected at the end of each period todetermine the concentration of leptin hormone in the breeders' blood. For comparison between mothers'performance, hormone concentration is separated into three groups: high, medium, and low, and according tothe interaction between body weight and leptin concentration to compare between mothers' performance.The results indicated a significant increase (p<0.05) in the concentration of cholesterol, high-density lipoprotein(HDL), low-density lipoprotein (LDL), very low-density lipoprotein (VLDL), and triglyceride (TG). Linearitybetween the studied traits and leptin concentration levels, by calculating the regression and correlationcoefficients, and adopting the hypothetical approach in estimating the prediction results to reach the bestpredictive values that approximate reality. We conclude from this study that body weight and theconcentration of leptin have unspecified effects on the serom chemical characteristics of laying hens.