The mean age of nurses was 27·2 years. Overall, 90·3% of nurses had back pain at least once a month (21·9% always, 40·7% once a week and 27·7% once a month). Only 18·3% had received medical treatment for their back pain. Compared with neonatal intensive care unit nurses, who had the lowest prevalence, nurses in other specialties, excluding paediatric intensive care units, had a greater likelihood of back pain. Specialty medical (e.g. cardiology, neurology) intensive care unit nurses had the greatest probability of back pain and treatment. Perceiving staffing as inadequate and working 6 or more night shifts per month were related to a 64% increase (OR = 1·64; 95% CI = 1·16–2·33) and 48% increase (OR = 1·48; 95% CI = 1·10–1·99) in back pain, respectively. Nurses with 2–4 years of working experience in intensive care units had the greatest probability of back pain and treatment.