Multitasking has been demonstrated to negatively impact performance across a wide range of tasks, including in the classroom, yet students continue to multitask. This study examined the relationship between college students' perceptions and performance of technology-based multitasking. Technology-based multitasking and self-efficacy data were collected and analyzed from 265 undergraduate students. Students engaged in a technology-based multitasking perceptions survey, a video + survey multitasking task or a video-only non-multitasking task, and a technology-based self-efficacy survey. An analysis of student perceptions indicated that students understood that different tasks required different levels of mental effort to complete successfully and that multitasking across high-mental effort tasks required greater effort than multitasking across low-mental effort tasks. In addition, students in the video + survey multitasking group significantly underperformed students in the video-only non-multitasking group. Finally, the relationship between technology-based multitasking and self-efficacy was addressed in a correlational analysis between student technology-based multitasking scores and technology-based self-efficacy scores, yielding no significant relationship. The study findings indicate that most students have an understanding and awareness of multitasking, but ultimately, whether they believed they could multitask or not, multitasking significantly impeded performance.