Millennials are the generation that lived in the era of information technology revolution with the emergence of the internet and smart phones. Because of this experience, millennial has become an important element for human resources to meet industry 4.0. However, it is not clear how older leadership behaves on this generation and what impact they have on organizational performance. Thus, this paper focuses on investigating the effect of openness on millennial employee style on leadership effectiveness and its impact on 4.0 organizational performance. Survey is conducted on 224 millennial employees working in various companies in Indonesia. Data are analyzed using Smart-PLS 3.0 based on structural equation modeling (SEM). Our results showed that openness to millennial employee style had a positive effect on 4.0 organizational performance partially mediat-ed by 4.0 leadership effectiveness in industrial settings. These results confirm the role of millennial in shaping organizational performance and how managers need to implement appropriate measures to manage millennials and be open to various characteristics of this generation.