This research could have significant implications for improving mental conditioning practices in sports. By establishing the validity of this questionnaire, researchers and coaches can better understand the relationship between self-talk and mental toughness, leading to more effective interventions and training programs that enhance athletes' resilience and competitive edge. This study aimed to validate its psychometric properties to detect the self-talk of athletes and how it affects their mental toughness. The participants were 93 Athlete in martial arts and game sports (83 Male and 10 Female with Age; M=24.35, SD=7.338) in Bekasi, Indonesian athletes. Data were collected randomly in an online form. Rasch analysis was utilized to evaluate the validity and reliability of the self-talk questionnaire in the Indonesian version with 5 Likert scales, and linear regression was used for hypothesis analysis. The results showed that the self-talk questionnaire in the Indonesian version achieved validity and reliability criteria based on Rasch parameters with five rating scales. The questionnaire data revealed strong positive connections between self-talk and mental toughness. Challenge had the largest effect on negative self-talk, while control had the largest effect on positive self-talk. In conclusion, self-talk has a significant impact on athletes’ mental toughness.