The Lean Startup Approach (LSA) is a framework for new venture creation based on five stages: finding and prioritizing market opportunities; designing business models; validated learning; building minimum viable products; persevering or pivoting with course of action. Despite its significance in reducing the risk of new ventures’ creation, the LSA remains underdeveloped. Further clarification is needed on the contingencies, represented by novel trends in contemporary practice, that can influence LSA’s applicability and effects. Accordingly, this paper unveils how Transformative Artificial Intelligence (TAI) acts as a contingency and influences the five stages of the LSA, by introducing new opportunities and boundary conditions. Through a multiple case study of five TAI-based startups, we retrieved how TAI acts as a first-level contingency and unlocks opportunities to initiate the LSA. Furthermore, we investigate how TAI acts as a second-level contingency and serves as a boundary condition influencing the entire applicability of the LSA.