Goal: The main goal of this research is to investigate whether athletes develop different personality traits than non-athletes and vice versa, and whether these differences are the result of natural selection or the influence of the sports environment. Methods: The research was conducted on a convenient sample (N=52) consisting of 26 athletes and 26 non-athletes (students of the Faculty of Health Studies of the University of Rijeka). The measuring instrument used in the research is the International Personality Item Pool – Five Factor Model – 50 (IPIP-Big5), a standardized questionnaire for the assessment of five main personality traits consisting of 50 statements to which the respondent expresses the degree of agreement or disagreement on a Likert scale. Results: The results showed that there are no significant differences in openness between athletes and non-athletes. In the domain of conscientiousness, it was shown that non-athletes have a slightly higher average value of conscientiousness compared to athletes, the data also show that conscientiousness in athletes is also highly developed. Non-athletes scored slightly higher in extraversion compared to athletes, although both groups show a high level of extraversion. Contrary to expectations, the data show that non-athletes have a slightly higher average value of pleasantness compared to athletes. However, athletes also show a high level of comfort. In the end, it turned out that athletes have lower values of neuroticism, which indicates greater emotional stability. Conclusion: The research showed that there are certain differences between athletes and non-athletes in some personality dimensions, but these differences are not statistically significant. The results showed that athletes have a slightly higher average level of emotional stability (lower neuroticism) compared to non-athletes, but this difference was not statistically significant. Similarly, non-athletes showed slightly higher levels of extraversion, agreeableness, and conscientiousness compared to athletes, but these differences were also not large enough to be considered statistically significant. This research confirms the complexity of the connection between personality traits and sports and highlights the need for further research.