The main drivers for this research are the complexities associated with the project management and an organization's project management style in dealing with these complexities. This research aims to demonstrate that alignment between project complexity and project management style increases project performance and decreases project issues, and also, with increased project issues, project performance deteriorates. In order to test these claims, this research developed measures for assessing project complexity, project management styles and project issues by employing a survey of project management professionals. The measure for project complexity is based on a taxonomy with four categories: organizational complexity, product complexity, methods (process) complexity and goal complexity. Project management style is defined as the management paradigm that guides the managers of an organization in perceiving and dealing with management problems. The measure for project nagement style is based on the plan-do-study-act (PDSA) cycle and the Newtonian and complexity paradigms. Also the measures for project issues are developed after an extensive content analysis on the literature on project issues, risks and success factors. A self-administered survey instrument (paper-based and on-line) with 40 questions (seven point Likert scale) was utilized. The respondents were the project management professionals from different industries in the Central Florida region. Each respondent was asked to answer questions for two different kinds of projects: a successful project and a challenged project. Based on the data collected by the survey instrument, the results of confirmatory and exploratory factor analyses provide strong evidence that the final measures for project technology complexity, project management styles, project issues and project performance have adequate validity and reliability. Results of the hypothesis tests demonstrate that increased alignment of project complexity and project management style leads to increased project performance and decreased project issues, and also increased project issues leads to project decreased performance. From the perspective of project management, the results of this study have illustrated the importance of aligning a project's complexity and management style. These results suggest that project or program managers can improve the performance of their projects by any attempt to increase the alignment between project complexity and project management style. Project management professionals and theoreticians can use the methodologies provided in this dissertation to assess project complexity, project management style and alignment.