This specialist thesis describes in detail the planning and programming of the mesocycle of the men's handball cadet national team of Croatia (U-19), which I planned and programmed as a coach, and finally implemented together with my professional staff in the summer of 2021. In the first part of the thesis, the general laws of planning and programming are presented as the basic structure for achieving the targeted results, and all individual periods within that structure are explained. Furthermore, the mesocycle of the preparation of the men's cadet handball team of Croatia for the European Cadet Handball Championship (EHF EURO M19), which was held in Croatia, is presented, and analysed in detail. Chronologically, it goes through the periodization procedure, analysing each individual phase, then through the presentation and analysis of the microcycle, and through the presentation of individual conditioning and handball training within the microcycle. The systematization and detailing of the described points to the complexity of the management action, such as the planning and programming of the mesocycle of the men's handball cadet national team of Croatia for the top level of competition. Some of the details to which special attention is paid are the technical-tactical aspect of preparations, the selection of the game system, the methodology of work in all phases of the handball game. then problems, challenges and adaptation of the preparation plan itself. Synergy and help from our best and most experienced trainers are shown as important factors in achieving the set goals and achieving top results. The European Cadet Championship itself is presented chronologically through all the championship matches, with an emphasis on careful planning and programming in correlation with the achievement of set goals.