The following paper highlights the theories used to further project management (PM) research spanning the 15 year time period of 1999-2013. The analysis examined 273 articles drawn from seven widely recognized PM journals with the aim of uncovering the most utilized theories in the discipline's academic investigations. The review found these theories to be: Stakeholder Theory (ST), Fuzzy Sets Theory (FST), Utility Theory (UT), Theory of Constraints (TOC), and Actor-Network Theory (ANT). This collection of theories represents a diverse group of thought constituting a large portion of the PM literature's theoretical foundations. Both UT and TOC have diminished in popularity while ANT and ST have improved in favor; FST has remained consistent in its use. The appendix to this manuscript includes a “ready reference” of all the theories utilized in PM research found within the reviewed journal outlets from the 15 year review period.