Music is increasingly used in a wide array of settings, from clinical recovery to sports or well-being interventions. Motivation related to music is often considered as a possible working mechanism for music to facilitate these processes, however this has not previously been systematically evaluated. The current systematic review considered studies that involved music (therapy) interventions, together with motivation-related measures such as wanting to practise, liking the musical activities, or patient adherence to an intervention. Our objective was to examine whether music is related to increased motivation in task performance and/or rehabilitation settings, and whether this is in turn related to better clinical or training outcomes. Seventy-nine studies met the inclusion criteria, the majority of which (85%) indicated an increased level of motivation with music as compared to without. Moreover, in those studies where motivation was increased, clinical or other outcomes were improved in most cases (90%). These results support the notion of motivation as an underlying mechanism of music-based interventions, but more robust evidence is needed to ascertain which mechanisms are crucial in increasing motivation from a behavioural, cognitive, and neurobiological point of view, as well as how motivational mechanisms relate to other factors of effectiveness in music-based paradigms.