Past research has shown that there is a relationship between body posture and cognitive processes. However, postures used with technological devices has not been studied more extensively. The purpose of this study was to examine posture effects when using a mobile device on interpretation bias, mood, and physical tension. Each participant was randomly assigned one of three conditions: sitting slumped, sitting upright, or lying down. Participants were asked to complete the Scrambled Sentences Task (SST), a task of unscrambling emotional and neutral sentences, to measure their interpretation bias. Additional questions were asked to measure the participant's physical tension and mood. Results suggested no significant differences in interpretation bias depending on posture. There was no significant difference in the performance of unscrambling emotional sentences compared to neutral ones for sitting slumped and sitting upright. When lying down, participants unscrambled fewer neutral sentences compared to emotional ones. Physical tension was found to be a mediator for the relationship between posture (slumped and upright) and mood. The results of this study provide insight of possible confounding variables influencing the relationship between posture and mood.It additionally showed that emotional content is processed differently compared to neutral content when lying down. Further research is needed to understand how physical tension caused by posture being altered when using mobile device affects psychological well-being.