Background: Peer assisted study sessions (PASS) is an international, widely adopted, supplementary instruction program that has shown to have multiple academic benefits for students. However, PASS attendance rates across the world are typically very low, and the reasons for this are unclear. Aim: (1) To test the predictability of the theory of planned behaviour (TPB) on PASS attendance and subsequently students’ academic performance; (2) To assess the role of students’ motivation within the TPB; e.g., can motivation close the intention-behaviour gap; (3) To test whether a large scale intervention based on the TPB can improve PASS attendance and subsequently improve students’ academic performance. Sample and Method: TPB measures, academic motivation, PASS attendance and final unit grade were assessed three times pre-intervention across two Australian universities (N=965) and modelled using Latent Variable Analysis. The intervention consisted of a series of ‘PASS Facts’ delivered to students (total N=2087) via multiple media. Results: The findings showed that the TPB predicted PASS attendance and performance. Academic motivation predicted performance, but it did not close the intention-behaviour gap nor moderate the PASS attendance-performance relationship. Furthermore, in all three implementations, the interventions did not increase the theoretical constructs. Conclusions: The TPB is useful for predicting PASS attendance and can be extended to predict students’ performance. Future research should investigate factors other than academic motivation to attempt to close the intention-behaviour gap. Future research may also develop a more active intervention, wherein students can practice a skill (i.e., time management) instead of passively receiving messages.