Many studies believe that regular physical activity can have immediate health benefits by positively affecting cardio respiratory, muscular fitness and body composition improvement. The main interest of the present study was to evaluate the effect of aerobic exercise on health related physical fitness variables. The study design was experimental research method. 34 male students of addisalem general secondary school aged17-20 years had divided by simple random sampling method into two equal groups, experimental (n=17) training group who performed aerobic exercise in three days/week for three months and a control (n=17) group however, did not perform this selected aerobic training. Both groups had taken pre and post-testing and all the subjects participated in 4 physical fitness tests: cardio respiratory fitness was measured using 12 minute run test, muscular endurance was measured by 900push up test, flexibility was measured using sit and reach test and Body Composition was measured using BMI. The data collected from the study subject was analyzed using SPSS version 23 software. By using paired sample t-test the mean difference changes from with level of significant at 0.05. The results showed health related physical fitness components such as CVE (MD=138.235, p=0.006), ME (MD=8.588, p=0.041), and Flexibility (MD=2.882, p=0.032) were improved significantly following the 12 week fitness Exercise in EG at (p<0.05). Besides, body mass index (MD=-0.702, p=0.004) were significantly improvement was seen, since (p<0.05). But, no significant fitness improvement were found in all selected variables of CG (p>0.05). Furthermore, the results of most health related fitness components of EG such as cardiovascular endurance (MD=-14.706, p=0.557), ME (MD, 1.059,p=0.269) flexibility (MD=-0.176, p=0.772) Generally, the present study concluded that aerobic exercise training had a significant effect on students’ physical fitness through selected physical fitness variables. Hence, aerobic exercise is effective and beneficial effect for the enhancement of male students’ physical