Navigation structure and user familiarity are critical for user satisfaction, yet the mediating mechanisms by which they affect satisfaction remain unclear, especially from a cognitive perspective. To extend understanding of the drivers of user satisfaction with a website, this study focuses on the mediating roles of cognitive load and performance outcomes (in the form of efficiency and accuracy) according to a cognitive cost–benefit framework and cognitive load theory. The hypotheses were tested with data from a field quasi-experiment among 238 participants using two websites. The results indicated that cognitive load and performance outcomes fully mediated the effect of user familiarity on user satisfaction, and that cognitive load partially mediated the impact of navigation structure. In addition, the mediating effect of cognitive load appeared stronger than that of performance outcomes. Overall, the cognitive cost–benefit framework sheds light on the underlying influence processes and mechanisms by which navigation structure and user familiarity affect user satisfaction. The findings reveal that costs might have more profound influences on user satisfaction in an information-seeking context than benefits do.