The transferability of a Mediterranean diet (MedDiet) in non-Mediterranean populations is appealing. However, little is known about the perceived enablers or barriers toward adherence, particularly in Australia. This study aimed to investigate the perceived beliefs, barriers, and enablers toward adherence to a MedDiet in Australian adults. Barriers and enablers were assessed using a self-administered online questionnaire, which included questions aligned with the Theory of Planned Behaviour (TPB). The survey was completed by n = 606 participants. Barriers and enablers toward adherence to MedDiet were grouped under the three core constructs of the TPB: attitudes (suitability, taste, restrictive, food waste); social norms (food culture); and perceived behavioural control (PBC) (motivation, affordability, time/effort, food access, knowledge, food outlets, natural conditions, cooking skills). PBC emerged as the most prominent construct influencing intention to follow a MedDiet. Perceived health benefits (n = 445; 76.5%) and improved diet quality (n = 224; 38.5%) were identified as major advantages. In contrast, dietary adherence (n = 147; 39.7%) was perceived as an important disadvantage. Future MedDiet interventions, in both research and clinical settings, should consider adopting strategies aimed at improving self-efficacy to reduce self-perceived barriers and facilitate dietary adherence.