Background Chronic kidney disease (CKD) is an important risk factor for cardiovascular diseases and mortality. Physical inactivity is a modifiable risk factor that may affect the development and course of CKD. It is well established that exercise improves a number of metabolic factors, as well as blood pressure and insulin resistance, which would be expected to preserve renal function and lower cardiovascular risks. Aim of the study The aim of this study was to investigate the effect of treadmill walking exercise (moderate aerobic exercise) on kidney function tests and lipid profile in patients with CKD stages 3 and 4. Patients and methods Fifty patients with CKD stages 3 and 4 participated in the study. They were selected from the outpatient clinic of Nephrology Department, Zagazig University Hospitals (during the period from January 2015 to June 2015). Their ages ranged from 45 to 55 years. They were divided into two groups: the study group (group B), which included 30 patients who received moderate aerobic exercises on treadmill three times per week for 3 months plus their medications, and the control group (group A), which comprised 20 patients who received their medications only with no training exercises. Urine and blood samples were collected for determining glomerular filtration rate (GFR), serum blood urea, serum creatinine, and serum lipid profile before the initiation of the training program and after the completion of the study (after 3 months). Results There was a statistically highly significant decrease in creatinine, blood urea, triglyceride (TG), cholesterol, and low-density lipoprotein (LDL), and an increase in GFR and high-density lipoprotein (HDL) (P<0.001) in group B after treatment compared with the pretreatment values with the following percent of improvement: creatinine −11.5%, blood urea −7.9%, TG −10.5%, cholesterol −13.1%, LDL − 11.9%, GFR +17.4%, and HDL +12.6%. However, there were no significant differences between pretreatment and post-treatment values of creatinine, blood urea, or GFR in group A. There was a significant decrease in TG, cholesterol, and LDL, and a significant increase in HDL in group A after 3 months, with the following percent of improvement: TG −2.9%, cholesterol −3.4%, LDL −5.6%, and HDL +6.7%. There was a statistically significant difference in the post-treatment values of all parameters between the two groups. Conclusion It can be concluded that moderate aerobic exercises improve kidney function tests and lipid profile and can delay progression of CKD stages 3 and 4.