Treatment retention is associated with better outcomes and reduced risk amongst people experiencing opioid use disorder (OUD). Despite this, treatment retention remains low amongst this population. We carried out an international cross-sectional survey of substance use disorder (SUD) treatment service workers. We aimed to understand the barriers to treatment retention in the context of OUD from the provider perspective, identify differences in response preference between professional groups, and describe regional differences in treatment provision. We report data from 497 respondents based in the USA and the UK. Personality disorders, low motivation to change and social problems were the most often reported obstacles to retention. Comorbid SUD, hepatitis and HIV were not reported as often as expected. We identified associations between professional groups and response preferences related to comorbid SUD, low motivation, living arrangements and communication difficulties. UK respondents used behavioural treatments more than their US counterparts. US respondents more often reported using objective methods of measuring retention such as urine analysis, compared to their UK counterparts. The findings from this survey suggest that regional differences exist between US and UK based SUD treatment service workers. Personality disorders represented the most often experienced obstacles to treatment retention amongst patients with OUD, with mental health and social problems more often reported than comorbid drug problems or physical health problems. Statistically significant relationships exist between professional group and obstacles reported. These data may be used to identify additional training needs amongst SUD treatment service staff.