Research Paper (postgraduate) from the year 2020 in the subject Health - Sports science, Haramaya University, course: Physical Fitness, language: English, abstract: The purpose of this study was to examine the effect of aerobic exercise on improving health related physical fitness component of Bistima town administrative office workers. The Purposive-random sampling technique was used to select 25 sedentary male office workers recruited as study subject from Bistima town administrative office. These 25 sedentary male subjects were assigned as one quasi experimental design and their age range were between 24-36 year .All selected subjects participated in low to moderate intensity aerobic exercise for 12 weeks (3month),3 days per week and 60 minute duration at 55-70 maximum heart rate (MHR) per day from November 2017-January 2018.Pre , during and post training test were conducted on selected variables of health related physical fitness components. The collected data was analyzed by paired sample t-test (SPSS v.20) to determine the mean differences value and to make comparison in between pre test and post test mean value results. The level of significant was 0.05. According to analyzed data in step test was 21.320 beat per minute (15.06%,p<0.01) mean difference were observed. The mean difference value boosted in push up performance by 5.160 number/minute (54%, P<0.001) after 12 week aerobic exercise training. In sit up and sit and reach test 6.36 number/minute (42.67%,p<0.01) and 7.680 cm (>143%,p<0.01) increment were observed respectively. But in body mass index 2.480kg/m2 (11.48%,p<0.01) decrement were observed throughout the study period. The result obtained in this study indicated that there were significant improvement in cardio vascular endurance, muscular endurance, muscular strength and flexibility and there were reduction on body composition. Based on this finding, it can be concluded that 12 week low to moderate aerobic exercise have positive effect on improvement of HRPF components of sedentary male office workers. So, different responsible bodies should take considerable action on the participation of the community on a regular aerobic exercise training program to reduce sedentary activities.