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 with two difficulty levels under conditions that emphasized either accuracy or speed. DDM parameters, which included drift rates, decision thresholds, non-decision times, and starting biases, were analyzed. We found consistent gender differences in decision thresholds when the task emphasized speed, rather than accuracy. Less consistent were gender differences in drift rates, though effects still tended to be more pronounced under time pressure. No gender differences in non-decision times or starting biases were consistently found. Implications of time pressure on gender differences in mental rotation performance are discussed in relation to affect and strategy.