That idea that problem-based learning (PBL) is more motivating that traditional education has been prevalent since the inception of PBL at McMaster University in the late 1960s. Evidencing this through empirical research, however, has proven to be a lot more problematic. This paper retraces how the discourse on motivation started from a laymen’s conception in the early days of PBL, and slowly evolved into a field of scientific inquiry in the 1980s and 1990s. However, looking at the evolution of motivation theory over the same period, we show that motivation discourse in the burgeoning literature on motivation and PBL remained largely wedded to the laymen’s approach, and failed to catch up with the new achievement-goal theory and self-determination theory approaches. This paper proceeds to analyse the explosion of studies on PBL and motivation after 2000, acknowledging efforts to move away from anecdotal accounts and provide theoretical grounding to the research. However, once again, we show that the majority of the research employed outdated motivational measures that do not fully grasp the complexity of contemporary motivation theory. The paper concludes on the observation that single-course and curriculum-wide research interventions have yielded no conclusive results on the effect of PBL on intrinsic motivation, and that future research should therefore seek to use up-to-date motivational constructs in more targeted interventions.