The current study aims to examine the influence of incorporating different emotional design approaches into multimedia on 7th grade middle school students' positive emotions, mental effort investments and learning achievements (recall and transfer). To this end, four different instructional materials were created. Each material was identical, with only the extent of emotional design differing. For the Neutral Design (ND) group, none of the emotional design principles were used (monochromatic grayscale). For the Colorful Design (CD) group, attention-grabbing, bright and saturated colors were added to the material. For the Anthropomorphic Design (AD) group, expressive facial expressions (anthropomorphism of lifeless objects and expressive facial expressions of human characters) were incorporated into the material. Finally, for the Anthropomorphic Design and Sound Effects (ADSE) group, interesting sound effects were also used. The study was conducted at a middle school with a group of 106 students. Positive emotions were measured using an emWave emotion detection device. Results revealed that positive emotions generally increased as the amount of emotional design features increased. However, while students who used the Colorful Design invested more mental effort compared to students who used the Neutral Design, students who used the Anthropomorphic Design and Sound Effects (ADSE) invested less mental effort compared to students who used the Colorful Design. In addition, students who used the Colorful Design outperformed students who used the Neutral Design in terms of their recall scores. No significant difference in terms of transfer of learning scores was observed across the groups. Results were discussed with respect to different views in the literature regarding the use of emotional design in multimedia.