Meta-analytical data provide evidence for a gender difference favoring males on mental rotation tasks, especially under time pressure. Why might time pressure exaggerate this gender difference? Here we used drift diffusion modeling (DDM) to inform our understanding of the potential mechanism(s) that underlie gender differences in mental rotation. Male and female adult participants performed a mental rotation task under conditions that emphasized either accuracy or speed. DDM performance-related parameters (e.g., drift rates and decision thresholds) were analyzed. We found that although men and women performed comparably when the task emphasized accuracy, there were robust gender differences in the speeded condition. Specifically, under time pressure, women exhibited slower drift rates and lower decision thresholds compared to men. We interpret these model parameters as reflecting differences in processing efficiency and response strategy, respectively. Implications of time pressure on gender differences in mental rotation performance are discussed.