Project complexity is a contributing factor to project performance. Understanding how project complexity interacts with management actions and project performance is imperative. This study fills this knowledge gap by empirically exploring the relationship between construction project complexity and project performance and their interaction with resource allocation. Empirical data were collected from 79 transportation projects. Due to its capability to build several regression models by adding independent variables to previous models, moderated hierarchical regression analyses were conducted to identify the underlying effect of resource allocation on the project complexity and performance relationship. The results show that: (i) project complexity was significantly correlated with schedule growth (positive correlation) but not significantly correlated with cost growth; (ii) resource allocation was significantly correlated with schedule growth (negative correlation) but not with cost growth; and (iii) resource allocation had a buffering effect where increasing resource allocation significantly decreases the effect of project complexity on schedule growth. The findings from this study contribute to the extant literature on construction project complexity by empirically showing that the impact of project complexity on schedule performance interacts with the level of resource allocation. This understanding of the role of resource allocation may help construction managers and engineers to better administer and manage their complex transportation projects. The findings also imply that organizations should appropriately evaluate project complexity to allocate necessary resources to achieve project success.