This study investigated the learners' satisfaction, motivation, and mental effort in Goal Based Scenario centered 3D multimedia learning environment (GBSc3DM). The design of the GBSc3DM was based on the Cognitive Load Theory (CLT) principles. Two versions of the GBSc3DM were developed. While Cognitive Load Theory principles were taken into account and implemented in the design of the first version (+CLT), those principles were not applied in the design of the second version (CLT). A total of 82 9th grade high school students participated in the study. Mixed methods were used to gather the data. The findings of the study revealed that the learners were satisfied with the Goal Based Scenario components and the CLT principles implemented in the first version of GBSc3DM. The learners pointed out that GBSc3DM and CLT principles motivated them to learn the topic. However, not only were the learners not satisfied with the second version (CLT), but they also found it distracting. The findings showed that the learners invested higher mental effort in the second version (-CLT) of GBSc3DM.