Background: A volitional help sheet (VHS) is an intervention for promoting implementation intentions. This study was the first to test the effectiveness of a VHS for increasing university students' lecture attendance. Aims: To develop a VHS to increase university students' lecture attendance and test its effectiveness at increasing the proportion of lectures attended, and promoting the maintenance of lecture attendance, over an 11-week teaching semester. Sample and Method: One hundred and seventy-eight undergraduate students enrolled in a psychology degree programme were allocated at random to a VHS or active control condition. Prior to intervention, measures of goal intention to attend lectures and trait conscientiousness were collected using self-report, online questionnaires. Over the following 11-week teaching semester, attendance at synchronous (live) online lectures was measured. Results: The VHS condition attended a greater proportion of lectures and maintained their lecture attendance for longer than did the active control condition. These effects were not sensitive to underlying goal intentions, although the sample means on the measures of goal intention were approaching ceiling. Trait conscientiousness increased the effects of the VHS on the proportion of lectures attended. Conclusions: VHSs constitute useful interventions for increasing and maintaining university students' lecture attendance.