Bhutan is a low-middle-income country with poor roads, rapidly increasing motor vehicle use and heavy alcohol consumption. We estimated the proportion of emergency department patients presenting with injury who had positive blood alcohol. We sought to breathalyse and interview all adult patients (≥18 years) presenting with injury at the Jigme Dorji Wangchuck National Referral Hospital in the capital city Thimphu, from April to October 2015. Breath tests and interviews were conducted with 339 (91%) of 374 eligible adult patients. A third (34%) were alcohol-positive and 22% had blood alcohol concentrations >0.08 g/dL. The highest alcohol-positive fractions were for assault (71%), falls (31%) and traffic crashes (30%). Over a third (36%) of patients had a delay of >2 h between injury and breath test. The results underestimate blood alcohol concentrations at the time of injury so the true prevalence of pre-injury alcohol impairment is greater than our estimates suggest. Countermeasures are urgently needed, particularly roadside random breath testing and alcohol controls.