The importance of the research lies in involving the process of developing core stability of the trunk muscles, as it treats the athlete's body as a single unit, specifically targeting the trunk muscles in basketball players. Therefore, the researchers wanted to explore this experiment. The research problem focused on the observation made by the researchers and their monitoring of most matches in the Iraqi Premier League, as well as their work as supervisors at the Al-Najaf Youth Forum and their observation of some local tournaments and league matches. They noticed that most coaches, whether national team coaches or club coaches, rely on a comprehensive training regimen for body muscles without paying attention to the deep trunk muscles (core stability) during their training application on the players, which leads to incomplete muscle strength in players, especially in the trunk area, and since it has a significant impact on mastering defensive skills. The research aimed to prepare exercises to develop core stability to strengthen the trunk muscles and some defensive skills for players under 16 years old in basketball, and to identify the effect of these exercises in developing core stability to strengthen the trunk muscles and some defensive skills for players under 16 years old in basketball. The researchers chose the experimental method using the two groups of experimental and control as it suited the research problem. As for the research samples, they were represented by basketball players at the National Center for Talent Care in Najaf Al-Ashraf, numbering (26) players, all of whom were selected for the experiment. The most important conclusion drawn by the researchers is that the development of flexibility, trunk strength, balance, and coordination positively reflected on the development of defensive movement and defensive follow-up performance. The main recommendations were the importance of using specific and targeted training to achieve defined objectives in developing basic stability according to standardized scientific principles to raise the training level of basketball players across various categories.