Interval training is an efficient training approach for developing players' match fitness and endurance levels .The purpose of this study was to investigate the effects of twelve week interval training on health related physical fitness in the case of Gissa high school u-17 male football trainers. The study employed True Experimental research design and comprehensive sample method its total population were 30 male students with the age of U-17(15-17) had divided randomly into equal groups at which group one got treatment with N=15 interval training and group two was a control group (N =15).Selected physical fitness variables were, muscular endurance, muscular strength, cardiovascular endurance and flexibility. Pre-test & Posttest measurements taken from the two groups before & after the experimental period of twelve weeks of interval training, which were performed three times per week. The researcher was used this test battery;(ninety degree pus up, wall sit, 12 minute run, and set and reach test) the test is valid, reliable and manageable and secure field test that can be used to monitor. The data collected from the participants were analyzed descriptive, paired t-test, with level of significant at p<0.05 by using SPSS version 26 software. Result indicated that the interval training had significantly improved in selected health related physical fitness variables, muscular endurance, muscular strength, cardiovascular endurance and flexibility. The result concluded as interval training methods show a better improvement on selected physical fitness variables twelve weeks interval training program of Gissa high school u-17 male football project players. The major findings in this study also suggest that the football-specific explosive Ninety Degree Push Up ,wall sit, 12 minute run test, sit and reach test can be utilized in the testing and identification of football players’ performance. Generally physical fitness level had a significant effect on players’ performance through the required tests. Hence, physical fitness quality training has been preferable for the enhancement of football player performance.