The regression results show that there is a significant indirect relationship between staff work engagement and innovative work behavior and task performance. In addition, there is a relatively positive relationship between the transformational leadership style and transactional leadership style of the department-level leaders in the Vietnamese public sector with staff work engagement, particularly innovative work behavior and task performance. On the contrary, laissez-faire leadership style negatively impacts staff work engagement and innovative work behavior. Staff work engagement is an integral part of the relationship between leadership style and leadership effectiveness. The findings suggest that the Vietnamese public sector should aim to identify transformational and transactional leaders. This research focuses on the department level and is limited to three leadership styles (transformational, transactional, and laissez-faire) only. 1. State the Research question 2. Describe the research problem 3. Identify the methods used