By focusing on the personalization principle, the present study investigates whether two different language presentation formats of a multimedia presentation influence students' learning outcome and how individual interest towards the learning material moderates this impact. German students (N = 104) were randomly assigned to either a conversational or a formal language format of the multimedia presentation that taught Gestalt Laws. The results of this study showed that there were more positive effects on the learning performance in the conversational presentation format than the formal language format. This was, therefore, an indication of the effects of personalization. Furthermore, individual interest is a significant predictor for learning in this study. By testing different percentiles of individual interest, the findings showed that students with intermediate interest were affected by the format of language style. In contrast, learning results of students with the very lowest and very highest individual interest were not affected by different language styles. These results underline the necessity to take into account individual motivational prerequisites when designing multimedia learning environments.