Leaders have a tremendous impact in driving employee's engagement at a higher level; and without engaged employees, it is impossible to achieve organizational goal. This book discusses the relationship between leadership styles and employees work engagement at the United Nations Economic Commission for Africa (UNECA) in ETHIOPIA. Descriptive correlation research design was used. A total of 39 leaders and 120 employees have participated in the study. The result showed that, there is a positive and significant relationship between transformational leadership behaviors and employees engagement (Vigor, dedication and absorption). However, the relationship was not strong enough which indicated very loose tie between the two parameters. Transactional leadership behavior had a strong significant and positive relationship with vigor, dedication and absorption. On the other hand, there was no statistically significant correlation between laissez-faire leadership behavior and employees engagement at UNECA.