Effective leadership is crucial for organizational success, influencing staff engagement and productivity. While various leadership styles exist, this study focuses on the impact of transformational, transactional, and laissez-faire leadership on staff work engagement within the Vietnamese public sector. The Vietnamese public sector is currently undergoing restructuring and reform, demanding leaders who can adapt to change and effectively engage their staff. Previous research consistently demonstrates a positive correlation between transformational and transactional leadership styles and work engagement across various cultures, while laissez-faire leadership often shows a negative correlation. However, research specifically examining department-level leaders in the Vietnamese public sector is limited. This study addresses this gap by investigating the relationships between these leadership styles and staff work engagement, focusing on innovative work behavior and task performance as key outcomes. The study aims to provide insights into optimal leadership styles for enhancing performance and engagement within the specific context of the Vietnamese public sector at the department level, a critical organizational unit with significant responsibilities.

Extensive research explores the relationship between leadership styles and work-related outcomes. Transformational leadership, characterized by idealized influence, inspirational motivation, intellectual stimulation, and individualized consideration, consistently shows positive correlations with employee engagement and performance. Transactional leadership, based on exchange and contingent rewards, also demonstrates generally positive effects. In contrast, laissez-faire leadership, marked by a lack of involvement and direction, is often associated with negative outcomes. Studies across diverse cultures and organizational settings support these findings. However, research on the Vietnamese public sector, particularly at the department level, remains limited. The existing literature highlights the need for further investigation into the specific impact of leadership styles on staff work engagement within this context, considering the ongoing reforms and the unique cultural nuances of Vietnam.

This study employed a quantitative research design using a cluster sampling method to select 378 participants from a training course for department-level leaders in Vietnam's Ministry of Culture, Sports, and Tourism. The data collection instrument was a survey questionnaire. Leadership styles were measured using the Multi-Factor Leadership Questionnaire (MLQ-5X), a well-established instrument for assessing transformational, transactional, and laissez-faire leadership. Work engagement was measured using the Utrecht Work Engagement Scale (UWES-9), a short form known for its reliability and validity across cultures. Innovative work behavior was assessed using a 9-item scale developed by Janssen (2010), and task performance was measured using a 3-item scale adapted from Kim (2014). Data analysis involved descriptive statistics, correlation analysis using Pearson's r, and linear multiple regression analysis to test the hypothesized relationships between leadership styles, work engagement, innovative work behavior, and task performance. The study also examined the mediating role of work engagement using regression analysis. The reliability of the measurement instruments was established using Cronbach's alpha, with values generally exceeding 0.7, indicating acceptable internal consistency. The structural model's validity was assessed using the standardized root mean squares residual (SRMR), with a value below 0.08 indicating good model fit. Statistical significance was set at p < 0.05 (one-tailed) or p < 0.01 (two-tailed), depending on the specific hypothesis being tested. The researchers utilized various statistical methods to evaluate the relationships between the variables, ensuring the robustness of the findings. The demographic characteristics of the participants were also analyzed to determine potential confounding factors.

The study revealed strong positive correlations between transformational leadership and innovative work behavior (r = 0.73), task performance (r = 0.61), and work engagement (r = 0.74). Transactional leadership also showed a significant positive correlation with task performance (r = 0.54) and work engagement (r = 0.78). In contrast, laissez-faire leadership demonstrated a significant negative correlation with work engagement (r = -0.46) and innovative work behavior (r = -0.34). Regression analysis indicated that transformational leadership style significantly and positively predicted work engagement (β = 0.51, p < 0.01), while transactional leadership significantly and positively predicted task performance (β = 0.34, p < 0.01). Laissez-faire leadership negatively predicted task performance (β = -0.23, p < 0.01). Furthermore, work engagement significantly mediated the relationship between leadership styles and both innovative work behavior and task performance. The analysis showed that work engagement explained 30% of the variance in innovative work behavior and 28% of the variance in task performance. These findings consistently support the hypotheses linking transformational and transactional leadership styles to positive outcomes and laissez-faire leadership to negative outcomes. The strength of the correlations and the mediating role of work engagement highlight the importance of adopting appropriate leadership styles to foster employee engagement and enhance organizational performance.

The findings of this study provide strong support for the positive impact of transformational and transactional leadership styles on staff work engagement, innovative work behavior, and task performance within the Vietnamese public sector at the departmental level. The results align with existing literature that emphasizes the importance of these leadership styles in various contexts. The significant negative effect of laissez-faire leadership underscores the need for active and engaged leadership to drive positive outcomes. The mediating role of work engagement highlights its crucial role in translating leadership styles into improved performance. This implies that leaders who effectively cultivate work engagement will likely see better results in terms of innovation and task completion. The study's findings are relevant to policymakers and organizational leaders in the Vietnamese public sector, providing empirical evidence to guide leadership development programs and selection processes. By focusing on developing leaders with transformational and transactional characteristics, organizations can improve staff engagement and achieve better performance.

This research contributes significantly to the understanding of leadership styles and their impact on work engagement and performance within the Vietnamese public sector. The findings strongly support the need for transformational and transactional leadership approaches while emphasizing the detrimental effects of laissez-faire leadership. The mediating role of work engagement is crucial and highlights the importance of fostering a positive and engaging work environment. Future research could explore the generalizability of these findings across different levels of the public sector, different sectors, and with other leadership styles. Further research could also examine the specific mechanisms through which leadership styles influence work engagement and explore cultural moderators that might influence these relationships.

This study's limitations include its cross-sectional design, which limits the ability to establish causal relationships. The reliance on self-reported data from questionnaires may also introduce potential biases. The focus on department-level leaders in a specific ministry limits the generalizability of the findings to other levels or sectors within the Vietnamese public sector. Future studies could address these limitations through longitudinal designs, the use of multiple data sources (e.g., observations, performance data), and broader sampling to increase generalizability. Finally, the study focused only on three leadership styles; including other styles may yield different results.