The purpose of this study is to investigate whether off-task multitasking activities with mobile technologies, specifically social networking sites and short messaging services, used during real-time lectures have an effect on grade performance in higher education students. Two experimental groups and one control group were used in this research. While participants in experimental groups 1 and 2 were allowed to navigate Facebook and to exchange short messaging service messages via mobile phones during real time in class lecturing, the control group participants were allowed to take notes using only pen and paper in the same lecturing conditions during three consecutive experimental sessions. The results showed that when students were given the opportunity of non-lecture-related multitasking using mobile phones writing/sending short messaging services and looking at Facebook profiles/reading news feed/looking at shared multimedia/reading wall messages during the lecture, their grade performance was hindered compared to traditional pen and paper note-taking. Engaging in social media use while trying to follow instruction may reduce learners' capacity for cognitive processing causing poor academic performance.