The research aims to study the effect of cluster training on the development of muscle power, speed of foot movements and the effectiveness of performing some offensive methods for junior kumite players in karate under 18 years old. The researcher used the experimental method by following the experimental design for the single experimental group using pre- and post-measurements. The research community is represented by junior kumite players in karate under (18 years old) in the Eastern Karate region and registered with the Egyptian Karate Federation for the 2022/2023 season. The basic research sample was chosen intentionally and included (14) juniors from the Pioneers Club in Tenth of Ramadan, in addition to (8) juniors from the same research community and outside the basic research sample to conduct the exploratory study and scientific transactions. The most important results of the research were that cluster training has a positive effect on the development of muscle power measurements and speed of foot movements for junior karate players under 18 years old, and that cluster training has a positive effect on the effectiveness of performing some offensive methods for junior kumite players in karate under 18 years, as well as the presence of improvement rates for the post-measurement over the pre-measurement for the research sample individuals in the tests under study, which ranged between (2.6%: 15.36%), and also the effect size values ranged between (0.62: 1.05), which indicates a medium to large effect size significance.