Media multitasking, characterized by simultaneous engagement in multiple media forms, is prevalent among university students within the personal learning environment. However, those who think they are capable of multitasking usually overestimate their ability to perform the actual tasks. This study examined university students’ learning performance from the perspectives of their media multitasking self-efficacy, perceived attention problems, and self-regulation strategies using the revised Online Learning Motivated Attention and Regulatory Strategies scale. Participants were 696 university students (275 males, 39.51%) in Taiwan. The author developed the media multitasking self-efficacy scale through open-ended interviews and pilot tested the measures using an exploratory factor analysis. The confirmatory factor analysis verified the uni-factor structure of the instrument. Second-order confirmatory factor analysis validated the two orthogonal higher-order constructs of perceived attention problems and self-regulation strategies as well as their subscales. Results from the multilevel structural equation model revealed significant negative indirect relationship between media multitasking self-efficacy and learning performance via both students’ perceived attention problems and self-regulation strategies. Study findings have implications for prevention and intervention of university students’ media-related attention problems and poor regulation strategy use within the personal learning environment.