Transformational leadership and project success: The mediating role of team-building D.A. Aga a , b , ⁎ , N. Noorderhaven a , B. Vallejo a a Tilburg School of Economics and Management (TiSEM), Tilburg University, Tilburg, The Netherlands b Ethiopian Civil Service University, Addis Ababa, Ethiopia Received 4 September 2015; received in revised form 15 December 2015; accepted 23 February 2016 Available online 4 April 2016 Abstract Although the effect of transformational leadership on project success is empirically supported, less is known about the mechanisms that explain this effect. To address this issue, we propose the mediating role of team-building as a possible explanation of the relationship between transformational leadership and project success. Based on a field survey of 200 development project managers in the Ethiopian Non-Governmental Organization (NGO) sector, the results of our study indicate that team-building partially mediates the effect of transformational leadership on project success. We discuss the theoretical and practical implications of these findings. © 2016 Elsevier Ltd. APM and IPMA. All rights reserved. Keywords: Project success; Team-building; Transformational leadership 1. Introduction Critical success factors (CSFs) are an important theme of research in the project management literature (Ika et al., 2012; Nauman et al., 2010; Söderlund, 2011). This branch of the literature has increased our understanding of factors critically influencing project success. One of the CSFs identified is the leadership style of the project manager, with specifically a positive effect of transformational leadership (Anantatmula, 2010; Lindgren and Packendorff, 2009; Riaz et al., 2013; Yang et al., 2010). Although previous research demonstrates that transformational leadership positively influences project success, there is scant work explaining the mechanisms underlying the relationship between transformational leadership and project success (Kozlowski and Ilgen, 2006; Piccolo and Colquitt, 2006; Yang et al., 2010). For instance, Piccolo and Colquitt (2006) point out that the underlying processes through which transformational leader- ship exerts its influences on project success have not been adequately addressed in the project management literature. Keegan and Den Hartog (2004) note that the positive effects of transformational leadership behaviors are weaker in a project context than for line managers, and they call for studies of factors moderating or mediating the relationship between transformational leadership and outcomes in order to acquire a better understanding. Similarly, Avolio et al. (2004) emphasize that a more concerted effort is required to explore the process and boundary conditions for transformational leadership leading to beneficial work behaviors. The present study seeks to contribute to a better understand- ing of the mechanisms through which transformational leadership behavior of project managers influences project success. Gundersen et al. (2012) call for more research to understand the relationship between transformational leader- ship and team performance through the use of mediators representing team processes. Similarly, a meta-analysis by Kozlowski and Ilgen (2006) identifies transformational leader- ship as a promising leverage point for enhancing team processes, such as team-building. Scholars like Scott-Young ⁎ Corresponding author at: Tilburg University, School of Economics and Man- agement, P.O. Box: 90153, 5000 LE Tilburg, The Netherlands. Tel.: +251 911839017. E-mail address: D.AssefaAga@tilburguniversity.edu (D.A. Aga). www.elsevier.com/locate/ijproman http://dx.doi.org/10.1016/j.ijproman.2016.02.012 0263-7863/00/© 2016 Elsevier Ltd. APM and IPMA. All rights reserved. Available online at www.sciencedirect.com ScienceDirect International Journal of Project Management 34 (2016) 806 – 818