Background Despite the paramount importance of oral health, individuals undergoing treatment for opioid use disorder face unique challenges beyond traditional addiction care. This qualitative study explores the challenges Opioid Treatment Program (OTP) clients in Australia encounter when accessing oral health care, aiming to understand the underlying factors and identify effective strategies for integrating oral health into an OTP. Methods Semi-structured interviews were conducted with OTP clients, OTP clinicians and oral health clinicians using tested interview guides. Thematic analysis identified patterns and themes across participants' responses. Results Client behaviour and traits such as inadequate health prioritisation, crisis-driven care and lack of motivation, shaped by a complex social environment, contribute significantly to inconsistent care and neglected oral health. Addiction exacerbates oral health issues as clients prioritise drug use over oral care and financial constraints, resulting in poor oral hygiene and a higher prevalence of dental problems. Psychological barriers such as dental anxiety deter clients from seeking care, while access issues including administrative burdens and system barriers, lost phones and unstable living conditions hinder consistent management of oral health. Stakeholders recommend actionable steps to address OTP clients' challenges, including integrating holistic care, establishing collaborative support systems, improving awareness and education and enhancing accessibility and flexible scheduling. Conclusion This study established a framework for improving OTP clients' oral health through integrated, holistic strategies. By addressing gaps in existing research, it supports the development of public health policies integrating oral health care into OTPs, aiming to foster collaboration, improve access and advance client education for better health outcomes.