A negative link between media multitasking and sustained attention has been proposed; yet, whether such a link exists remains hotly debated as previous studies found mixed effects. The present study seeks to evaluate the size of this effect taking into account possible variations due to how media multitasking is measured, how sustained attention is assessed, and the origin of the samples. Using an established and a novel, shortened measure for media multitasking, 924 participants were recruited through three different platforms (MTurk, Prolific and university students). In addition to questionnaire- and task-based assessments for sustained attention, impulsivity and sensation seeking were also assessed to further qualify behavioral problems associated with media multitasking. The findings establish a negative link between media multitasking and sustained attention of a medium effect size, whether questionnaires (r =.20) or a task-based measure (r =.21) are used. Importantly, the findings support the notion that previous differences across studies can be at least partly attributed to the choice of media multitasking measure as well as differences across samples.