Eating a plant-rich diet is considered essential for human and planetary health and the Mediterranean diet offers a realistic way to increase this. Gaining greater knowledge of the barriers and drivers to consuming the Mediterranean diet in residents of high-income countries was the aim of the current study. Semi-structured interviews were conducted with 16 adults residing in Australia who ate either an omnivore or plant-rich diet. Using reflexive thematic analysis (RTA) and the behaviour change wheel (BCW), an in-depth exploration of these barriers and drivers was conducted. Key barriers were: (1) changing ingrained meat habits, (2) lack of physical and mental availability, (3) household influences, (4) meat perceived as tasty and Mediterranean diet foods as bland and (5) minimal knowledge of the nutritional benefits of Mediterranean diet foods. Our findings emphasize the need to consider multiple individual and environmental barriers when designing behaviour change interventions to increase Mediterranean diet adoption.