This study investigates key livestreaming factors that affect consumers' willingness to pay, focusing on perceived usefulness and its components including personalization, streamer influence, interactivity, and number of views. The study also explores the moderating roles of trustworthy practices and promotional programs. A quantitative survey was conducted with 527 Vietnamese respondents who had prior experience with livestream shopping. Structural Equation Modeling (SEM) was employed to examine the relationships among the variables and to test the moderating effects of trustworthiness and promotional incentives. The results show that personalization, streamer influence, interactivity, and perceived usefulness significantly increase consumers’ willingness to pay. Furthermore, trustworthy practices and promotional programs positively moderate the relationship between perceived usefulness and willingness to pay. However, the number of livestream viewers was found to have no significant effect on perceived usefulness, suggesting that consumers are more influenced by content quality and engagement rather than social proof. These findings offer practical implications for e-commerce platforms, brands, and streamers. Stakeholders should prioritize building trust, enhancing real-time interaction, and delivering personalized content to drive purchase behavior.