Oil and gas drilling projects are the primary means by which oil companies recover large volumes of commercially available hydrocarbons from deep reservoirs. These types of projects are complex in nature, involving management of multiple stakeholder interfaces, multidisciplinary personnel, complex contractor relationships, and turbulent environmental and market conditions, necessitating the application of proven project management best practices and critical success factors (CSFs) to achieve success. Whereas there is a CSF approach to managing complex projects in construction, manufacturing, and even R&D, there is no empirically verified project management CSF approach to implementing (complex) oil and gas drilling projects. Additionally, the literature has reported alarming rates of oil and gas drilling project failure, which is attributable not to technical factors but to failure of project management. The aim of this two-part quantitative correlational study therefore, was to discover an empirically verified list of project management CSFs, which consistent application leads to successful implementation of drilling projects. The study collected survey data online, from two randomly derived samples of oil and gas drilling personnel: Members of LinkedIn's online community "Drilling Supervisors, Managers, and Engineers". A total of 219 Drilling Personnel (Drilling Engineers/Superintendents, Drilling Supervisors, and Drilling Managers) participated in the study, including 127 partcipants in the initial study and 92 in the follow-up study. The results of the study indicated that 12 project management critical success factors are individually related to success of oil and gas drilling projects. These 12 project management CSFs, are namely; Clarity of project goals & objectives, Top management support, Front-end project planning, Integrated stakeholder & supplier management, High caliber project personnel/Project team integration, Use of appropriate tools & technology, Integrated change control, Shared success criteria, Iterative monitoring & control, Communication, Use of realistic estimates, and Iterative risk management. In addition, the study found that the relationship between the 12 CSFs and drilling project success is unaffected by, and generalizable beyond participant and project demographics, namely; role designation of project personnel, project location, and project type (onshore or offshore). The significance of these findings is both practical, and theoretical. Practically, application of an empirically verified CSFs list to oil and gas drilling projects could help oil companies improve the performance of their drilling projects. Theoretically, the study's findings have helped to bridge a gap in the project management CSFs literature, and added to the general project management body of knowledge.