Introduction: Core stability is the ability to control the position and motion of the trunk over the pelvis and legs to allow optimum production and transfer the force to the terminal segment in sport activities. The role of core stability in lower extremity performance has been evaluated in some studies. However, results of such studies contradict each other. In this respect, it has been previously shown that studying the effect of core muscle fatigue on lower extremity performance can provide useful information about its critical role in lower extremity function. Therefore, the purpose of this study was to investigate the effect of core muscle fatigue on measurements of lower extremity functional performance in male athletes.Materials and Methods: Thirty-four healthy male physical education and sport sciences students participated in this experimental study. They all read and signed the consent form. Participants carried out the lower extremity functional performance tests including Y balance, side-to-side hop, figure-eight hop and triple hop in non-fatigued condition during first session. In the second session, at first, athletes participated in the core fatigue protocol consisting of seven exercises and immediately did the lower extremity functional performance tests. Paired t-test was used to compare the data in SPSS software, version 20.Results: Core fatigue protocol caused a significant reduction in the scores of all lower extremity functional performance tests including Y balance, side-to-side hop, figure-eight hop and triple hop (P=0.001 for all tests).Conclusion: Based on the results, it can be concluded that the core muscle function affects lower extremity performance, as core muscle fatigue resulted in decreased scores in all lower extremity functional performance tests in this study. Given the possibility that core muscles may become fatigued during long sporting events, training programs which increase core muscle endurance and improve their ability to resist fatigue, could probably be suggested as a way to prevent reduction of lower extremity performance during prolonged sporting activities.