Out of hours (OOH) doctors can have an important gate-keeping role over the access to the emergency department (ED), but the outcome and the quality of their ED referrals have been poorly studied. We aimed to investigate the outcome of patients referred to ED from OOH service and the determinants of admission or short-stay dispositions. We collected retrospectively data about referrals to ED from a local OOH service in the north-east of Italy using the OOH paper register and the ED electronic database, over the period of 01/10/2012 to 31/03/2013. Out of 5217 patients accessing the OOH service, 408 referrals were included in our analysis. 45.3% (185) of the referrals were admitted to hospital or the short-stay unit, 26 patients (=6.4%) were discharged as non-urgent outgoing codes after no specialist consultation or test, suggesting inappropriate referrals, and, of the remaining 197 (=48%), only 10 did not undergo any investigation or consultation. Significant determinants of admission were: age ≥65 years (OR = 2.619; 95% CI 1.528–4.491, p < 0.0001), domiciliary examination (OR = 2.168; 95% CI 1.353–3.476, p = 0.001), nursing home/palliative care setting (OR = 2.563; 95% CI 1.228–5.351, p = 0.012) and OOH triage code, ranging from an OR of 7.47 (95% CI 3.028–18.433) for minor urgencies to an OR of 26.835 (95% CI 6.761–106.508, p < 0.0001) for emergencies, in comparison to no urgent codes. OOH service seems to play an effective gate-keeping role limiting ED access. Determinants of admission to hospital suggest some simple interventions that could improve the adequacy of ED referral from OOH service. © 2017, SIMI.