The present study examines whether the seductive-details effect is moderated by spatial ability and prior knowledge, which are two of the most relevant learner characteristics in multimedia learning. It is assumed that the seductive-details effect with an increase in extraneous cognitive load and a decrease in perceptual processing and learning success is only present for learners with low spatial ability and low prior knowledge. To this end, the present study uses an Aptitude-Treatment-Interaction Design with separate analyses for spatial ability and prior knowledge as aptitude-variables and seductive details (with vs. without) as treatment-variable. Participants (N = 50) were asked to learn about biology with a multimedia instruction that manipulated seductive details. The results show that learners perceptual processing, measured by eye-tracking, and learning performance was significantly lower when learning with seductive details. In addition, spatial ability and especially prior knowledge were confirmed to play the expected moderating role.