The success of start-ups is strongly influenced by transformational leadership, which fosters innovation, resilience, and long-term sustainability. This study examines the relationship between transformational leadership and start-up success, emphasizing the mediating role of social impact and the significance of inspirational motivation. Using a quantitative research approach, this study involves young entrepreneurs across Malaysia. Findings reveal that transformational leadership has a strong positive relationship with start-up success. Additionally, social impact serves as a partial mediator, contributing 45% (0.45) to start-up success, indicating that while transformational leadership is a key driver, its effectiveness is enhanced when leaders integrate social responsibility and sustainable business practices. Among transformational leadership constructs, inspirational motivation emerges as the most significant predictor of start-up success. These findings align with Sustainable Development Goal (SDG) 8: Decent Work and Economic Growth, underscoring the need to embed transformational leadership principles into entrepreneurship education, leadership development programs, and policy frameworks to enhance start-up sustainability, drive economic resilience, and foster social impact.