"Appropriate self-regulation in motivation and experiencing flow in learning and other academic activities are important factors for success in study and psychological wellbeing. Previous studies suggested that achievement goals have role in student’s motivation for learning, but there is only partial knowledge regarding the role of achievement goals in motivational regulation and academic flow. The aim of this study was to explore: a) the role of achievement goals in motivational self-regulation and study-related flow; b) the incremental role of mastery self-talk motivational strategy in academic flow over the mastery-approach goal; c) the mediating role of mastery self-talk motivational strategy in the relationship between mastery-approach goal and academic flow. It was expected that both mastery-approach goal and mastery self-talk motivational strategy will have positive and incremental role in academic flow, and that the relationship between mastery-approach goal and academic flow would be mediated through using motivational strategy of mastery self-talk. The participants were 113 university undergraduate students studying mathematics (M= 20 years, 61% females). Self-report questionnaires assessing achievement goals, strategies used for self-regulation of motivation, and study-related flow were applied. Data analysis included regression analyses and mediational analyses. Regression analyses revealed that personal goal achievements explained 43% of variance in mastery self-talk strategy, 32% of variance in performance-approach self-talk strategy, 18% of variance in performance-avoidance self-talk strategy, 11% of variance in environmental control strategy, 7% of variance in self-consequating strategy, and 10% of variance in proximal goal strategy. Personal achievement goals explained 45% of variance in academic flow. Mastery-approach goal was predictive for explaining individual variance in most of positive motivational strategies and academic flow. In line with hypothesis, it was found that mastery self-talk mediated the relationship between mastery-approach goal and flow. The results underscore the importance of adopting mastery-approach goal and using mastery self-talk strategy in order to experience study-related flow."