Gambling is an activity that for some can become disordered, with severe negative consequences. Existing literature does little to inform us regarding changing gambling habits of treatment seeking gamblers; the current study sought to measure trends and patterns in UK treatment seeking gambler behaviour and demographics over a 15-year period.Case files for 768 gamblers seeking residential treatment with the Gordon Moody Association (GMA) were analysed, collected between 2000 and 2015. Case files comprised initial assessment questionnaires, demographic data, current gambling behaviour, mental and physical health status, and a risk assessment. Chi-squared analyses were used to measure change in categorical distribution.Prevalence of different forms of gambling identified as problematic have changed over time: Fixed Odds Betting Terminals (FOBTs), sports betting, and poker have become more common; horse and dog racing, and the National Lottery have become less common. Online gambling has also increased over time. In more recent years, gamblers are also more likely to have attempted suicide, to report a co-occurring mental health disorder, and to start treatment having already been prescribed medication.This is the first study to demonstrate that UK treatment seeking gambler behaviour has changed over time; major changes relate to the forms of gambling engaged in problematically, and the mental health of disordered gamblers. Whilst much media focus is directed towards one form of gambling, this should not detract focus from other forms and associated disorders, and the impact of the legislative environment.