Background: Mental training is based on the premise that psychological factors enhance or deteriorate performance and that these psychological factors can be optimized by training. Researchers have developed different methods to measure these factors, including behavioral tests and questionnaires. The Sport Mental Training Questionnaire (SMTQ) is a novel and multifaceted psychometric scale with 20 items developed to assess sports mental training across 5 dimensions, including foundational skills, performance skills, interpersonal skills, self-talk, and mental imagery. Objectives: The present study evaluated the validity and factor structure of the Persian version of SMTQ. It aimed to adapt SMTQ to Persian to present the validation of the scale in the sports context. Methods: The original version of SMTQ was translated and back-translated into Persian based on the established guidelines, followed by a pilot study. A total of 364 athletes (mean age = 26.27 ± 9.27) participated in this research, of whom 218 (59.90%) were male, and 146 (40.1%) were female. The participants were recruited using a web-based survey. Descriptive statistics, Cronbach α coefficient for internal reliability, confirmatory factor analysis (CFA), and independent t test were used to evaluate psychometric properties. Results: None of the items of the 20-item questionnaire were removed. The results supported the reliability of the Persian version of SMTQ (Cronbach α = 0.84). CFA supported its validity, the model fitted the data well (χ2/df = 2.15; root mean square error of approximation (RMSEA) = 0.056, Tucker-Lewis index (TLI) and comparative fit index (CFI) > 0.9; parsimonious CFI (PCFI) = 0.751). We supported the Persian version criterion validity of SMTQ by showing that high-level athletes scored higher on all mental training subscales than low-level athletes. Conclusions: The findings support that SMTQ is a reliable and valid instrument to assess mental training among Iranian athletes.