The task assigned was to clarify and objectify the impact of changing coaches during the season on the competitive results of individual handball teams. The aim was to shed light on this area and emphasize the importance of choosing suitable coaches for specific teams, which should ensure long-term success at the highest level. We examined the influence of coach changes in the 1st Slovenian handball league and the European Champions League between the 2012/13 and 2021/22 seasons. The gathered data was classified into three categories, and we analyzed the performance of old and new coaches. We calculated the success quotient, which is the number of points won divided by the number of matches coached. We found that 15 % more coaches were replaced in the 1st SRL compared to the EHF CL. The reason for this is seen in the greater stability of teams competing in the EHF CL, which experience fewer fluctuations in their performance. We also examined the short-term and long-term consequences of changing coaches during the season. We discovered that in both cases, replacing the head coach does not bring about changes in performance. Based on our findings, we advise Slovenian clubs to take inspiration from the best European clubs, make smart choices in selecting their coaches, assemble quality teams with them, and have confidence in their decisions. Changing coaches during the season should be reserved for serious reasons, as there is no evidence that such changes improve a team's success.