Gambling and substance use disorders often co-occur. Professionals who work in drug and alcohol treatment services have a unique opportunity to identify clients who are also dealing with gambling harms. However, little is known about the barriers they face for identifying and referring these clients to gambling-focused treatment. This study explored barriers for addressing gambling harms among professionals working in drug and alcohol treatment services in the North East of England. A total of 34 participants were interviewed. The researchers identified five themes: lack of training or awareness increases the hidden harm, stigma is a barrier, gambling is not a priority for management, treating gambling harms is not part of the mandate, and not asking about gambling means that no one receives help.