BackgroundTreatment for opioid dependence in Ireland is provided predominantly by general practitioners (GP) who have undergone additional training in opioid agonist treatment (OAT) and substance misuse. The National Methadone Treatment Programme (MTP) was introduced in 1998, and was designed to treat the opioid dependent population and to regulate the prescribing regimes at the time. The past two decades have seen the increased prescribing of methadone in primary care and changes in type of opioid abused, in particular, the increased use of over the counter (OTC) and prescription medications. Despite the scaling up of OAT in Ireland, drug related deaths however have increased and waiting lists for treatment exist in some areas outside the capital, Dublin. Two previous MTP reviews have made recommendations aimed at improving and scaling up of OAT in Ireland. This study updates these recommendations and is the first time that a group of national experts have engaged in structured research to identify barriers to OAT delivery in Ireland. The aim was to explore the views of national statutory and non-statutory stakeholders and experts on current barriers within the MTP and broader OAT delivery structures in order to inform their future design and implementation.MethodsA single focus group with a chosen group of national key stakeholders and experts with a broad range of expertise (clinical, addiction and social inclusion management, harm reduction, homelessness, specialist GPs, academics) (n = 11) was conducted. The group included national representation from the areas of drug treatment delivery, service design, policy and practice in Ireland.ResultsFour themes emerged from the narrative analysis, and centred on OAT Choices and Patient Characteristics; Systemic Barriers to Optimal OAT Service Provision; GP Training and Registration in the MTP, and Solutions and Models of Good Practice: Using What You Have.ConclusionThe study identified a series of improvement strategies which could reduce barriers to access and the stigma associated with OAT, optimise therapeutic choices, enhance interagency care planning within the MTP, utilise the strengths of community pharmacy and nurse prescribers, and recruit and support methadone prescribing GPs in Ireland.Electronic supplementary materialThe online version of this article (10.1186/s12875-018-0792-8) contains supplementary material, which is available to authorized users.