The striking gaps in formal mental health care in the developing world are largely traceable to Instrumental and Ideological Barriers. Focusing on south-eastern Nigeria, the study aimed to establish the relative weight, significance and determinants of these barriers for prioritised policy interventions. Multistage sampling method was used to select participants (n = 706) to whom questionnaires were administered. Ideological Barriers (cultural and mental health literacy constraints) were more significantly perceived (84.8%) than Instrumental Barriers (systemic and financial impediments) (56.6%). The study demonstrated the primacy of improved knowledge in plugging the gap in conventional mental health care in a region ironically defined more by systemic and material poverty. This is instructive for prioritised policy interventions with an indication that even if facilities and socio-economic status improve, services will likely be underused without greater improvement in people's conceptualisation of mental illness. It equally underscored the need for cultural competence in mental health service provision.