The study investigates the impact of user-generated content (UGC) on the purchase intention (PI) of ChatGPT Premium among undergraduate students, focusing on the mediating roles of brand attitude (BA) and brand trust (BT) by using SOR and HOE models. Using quantitative research methods and analyzing data from 105 undergraduate students who using TikTok in Malang City, Indonesia. Data analysis using SEM-PLS, and the results show that user-generated content has no direct effect on purchase intention. Meanwhile, user-generated content has a direct positive and significant effect on brand attitude and brand trust. Each brand attitude and brand trust also have a significant positive effect on purchase intention. Positive UGC can increase brand attitude and brand trust as well as increase interest in purchasing premium ChatGPT. Furthermore, based on the results of the indirect effect, it is known that brand attitude and brand trust can mediate the influence of user-generated content on purchase intention, where both act as full mediators in this research. This paper offers valuable insights into how UGC on platforms like TikTok influences consumer behavior in the context of freemium to premium transitions.