Tourism, as botth economic and social driver, has brought about significant transformations in digital marketing and human interactions. Accordingly, this study aimed to examine the impact of social media marketing on tourism- supportive behaviors, with the mediating roles of destination attractiveness and attitudes toward the positive effects of tourism in the city of Mashhad. This research is applied in nature and employs descriptive–survey design for data collection. The statistical population consisted of residents of Mashhad, and a total of 405 individuals were selected using a non-probability convenience sampling method based on Morgan’s table. Data were collected through a standardized questionnaire, whose reliability was confirmed using Cronbach’s alpha. Construct validity and face validity were also assessed,indicating that the instrument was both reliable and valid. Data analysis was conducted using structural equation modeling (SEM) with SmartPLS software version 3. The findings revealed that social media marketing has a significant positive effect on destination attractiveness, attitudes toward the positive effects of tourism, and tourism-supportive behaviors in Mashhad. Furthermore, destination attractiveness significantly and positively influences attitudes toward the positive effects of tourism and tourism-supportive behaviors, while attitudes toward the positive effects of tourism also have a significant positive effect on tourism-supportive behaviors. Finally, both destination attractiveness and attitudes toward the positive effects of tourism mediate the relationship between social media marketing and tourism-supportive behaviors in Mashhad.