Construction projects are complex as various project entities involve and collaborate with each other. This complexity not only causes issues such as project delays but also makes it difficult to manage projects. Previous research has often used productivity and efficiency interchangeably, but they are not the same. The field of construction efficiency has not been fully studied to understand its entire potential in a practical context. Toward this end, this research aims to support efficient construction project management by exploring the inefficiency factors as well as identifying the perception gaps between different occupations and the interrelationships between the factors. Twenty inefficiency factors were identified through a comprehensive literature review; then, the importance of the factors and the perception gaps among stakeholders were studied by analyzing online survey data using RII (relative importance index), Welch’s t-test, and factor analysis. In addition, interviews with field engineers and managers allowed us to explore cause-and-effect relationships among the factors and determine triggering and critical factors based on their chain reactions. This research found that a major perception gap among project stakeholders was in the factor of unrealistic scheduled dates. The research contributes to project risk management and strategic planning for construction project efficiency.