Aim <p>Problematic gambling is a significant global public health issue. This study examined factors influencing professionals’ decision to discuss gambling in healthcare and social-assistance settings. Adopting the theory of planned behaviour (TPB) to inform the proposed behavioural model, this study investigated whether attitudes, subjective norms, perceived behavioural control (PBC), and knowledge of gambling harm predicted professionals’ intentions and behaviours in talking about gambling with their clients supplemented by qualitative interview data.</p> Methods <p>Participants for both the survey (Study 1) and interviews (Study 2) were recruited using a mixed-network sampling approach, targeting professionals working internationally with clients who may experience gambling harms (e.g., general practitioners, social workers). Study 1 participants completed a survey (<i>n</i> = 89) assessing TPB constructs, knowledge of gambling harm, and demographics. Interview transcripts from Study 2 participants (<i>n</i> = 17) were analysed using content analysis.</p> Results <p>Survey data showed that intentions to talk about gambling were significantly predicted by perceived opinions of colleagues and PBC. PBC also directly predicted whether professionals spoke with clients about gambling. Analysis of interview data revealed that a lack of knowledge about problem gambling screening techniques and referral pathways were barriers. Organisational constraints, underfunding, and the urgency of addressing more immediate concerns reduce professionals’ motivation and capacity to screen for gambling problems.</p> Conclusion <p>The study highlights the need to raise awareness of how to talk about gambling and to which clients, and ensure professionals feel confident and capable of initiating gambling conversation. Interventions may include targeted professional education and skills-training programs within professional organisations.</p>