The primarily purpose of this study was to investigate the effect of 12weeks aerobic exercise on cardiovascular and muscular endurance performance of students at Addiskidam Secondary and Preparatory School .To determine the target population the researcher were used purposive sampling methods and to attain the objective of the research 28(14male and 14female) subjects were selected by using simple random sampling method to determine as control and experimental group for the study from the total number of 160 grade 11 students. The control groups did not involve in aerobic exercise program but experimental group was participated in moderate intensity aerobic exercise for 12 consecutive weeks with frequency of 3 days per a week for40- 60 minutes. Subjects mean of age ± 18 years and variables for the study were cardiovascular endurance and muscular endurance. Pre- and post-test were conducted to measure the selected variables. The data were collected by using physical fitness tests and to attain the objective of the study experimental design was used and data were analyzed by using paired sample t-test and two tail hypothesis tests from the SPSS version-20 were implemented. To assess and compare the experimental and control groups PT and POT in CVE and ME performance by formulating alternative and null hypotheses to accept or reject. When we compare the mean value the experimental group showed better significant improvement from PT to POT, but not in the control group. The finding of this study showed that, aerobic exercise program has a positive effect on cardiovascular and muscular endurance status of participants. Based on this the researcher recommend that students should participate in regular aerobic exercise in order to improve their fitness level.