We estimated proportions of different types of diabetes, comorbidities, treatment (the use of oral glucose-lowering agents and insulin), control (hyperglycemia, dyslipidemia and hypertension) and chronic microvascular and macrovascular complications among people with diabetes presenting to the tertiary-care academic diabetes outpatient clinics in Iran. This study is the prospective analysis of data (n = 30,202) from the registry of university-affiliated adult outpatient diabetes clinics in the country during 2015–2016. The proportions of type 1 diabetes, types 2 diabetes, and other types of diabetes were 11.4%, 85.5%, and 1.3%, respectively. The frequencies of drug-naivety, use of oral agents, insulin monotherapy and insulin combination therapy were 2.9%, 60.5%, 11.5%, and 25.1%, respectively. Around 13.2%, 11.9% and 43.3% of patients with diabetes had controlled hyperglycemia, hyperlipidemia and hypertension, respectively. The proportions of retinopathy, nephropathy, peripheral neuropathy, diabetic foot, and ischemic heart disease were 21.9%, 17.6%, 28.0%, 6.2%, and 23.9%, respectively. Despite the wide availability of medications and insulin coverage in Iran, the estimated national control of hyperglycemia, hyperlipidemia and hypertension (especially for young men and old women) remains subpar. The present study further suggests that the frequencies of chronic vascular complications among patients with diabetes are relatively high in Iran.