Abstarct: Social media addiction is a growing problem with social, physical, and psychological effects on athletes. Therefore, it is essential to develop prevention strategies to promote the safe and healthy use of social media sites such as Instagram. This study examined the effect of stimuli on Instagram addiction among athletes with the moderating role of psychological well-being. It was applied, correlation-guided research conducted in descxriptive terms of method. The statistical population of this research consisted of only 250 athletes from Shahrood City. The sample size was determined using the G*power software. Data were collected using a 20-item questionnaire by Pounosamy et al. (2020) to measure stimuli (cognitive needs, informational needs, social needs, and entertainment needs), a 6-item questionnaire by Sholeh & Rusdi (2019) to measure Instagram addiction, and a 3-item questionnaire by Pounosamy et al. (2020) to measure psychological well-being, which was designed on a five-point Likert scale (1=Strongly disagree to 5=Strongly agree). After confirming the criteria of Cronbach's alpha, composite reliability, and the divergent and convergent validity of the research variables, in the structural model fitting section, the results of the analysis showed that the need for recognition, information needs, and social needs and psychological well-being had a positive and significant effect on athletes' Instagram addiction. However, entertainment needs do not have a significant positive effect on Instagram addiction. Additionally, psychological well-being does not moderate the relationship between stimuli and athletes' Instagram addiction.