Purpose– The purpose of this paper is to provide new insights into the diet and nutrient intake of people receiving opioid agonist treatment (OAT) in the UK, offering implications for recovery-oriented treatment and care.Design/methodology/approach– Diet and nutrient intake were assessed using quantitative methods. The research tools used were: a socio-demographic and drug use questionnaire, 24-hour dietary recall interview and anthropometry measures. A four-month follow-up was conducted using the same methods.Findings– Mean (SD) body mass index for males (n=15) and females (n=10) exceeded the normal range (25.2 (5.9) kg/m2 and 33.3 (8.6) kg/m2, respectively) at baseline. Males decreased to the normal range at follow-up (mean (SD)=24.1 (±6.2) kg/m2]. Females increased to obesity Class II at follow-up (mean (SD)=35.1 (±8.0) kg/m2). Non-starch polysaccharide intakes were significantly lower than the reference nutrient intake (RNI). Iron intakes for females were significantly below the RNI. Saturated fat intake and sodium intake exceeded the RNI. In total, 11 (44 per cent) participants had multiple health conditions. Participants regularly consumed meals and reported frequent snacking events.Research limitations/implications– There is a need for better understanding of nutrition-related issues and dietary deficiencies amongst people receiving OAT, including larger studies that explore differences between males and females, other sub-groups and changes over time.Practical implications– Nutritional recommendations or guidelines and increased attention to nutrition and diet within treatment programmes are needed to help people receiving OAT.Originality/value– This paper demonstrates how diet and nutrient intake are essential to recovery processes and outcomes.