The provision of professional interpreting services (PIS) in the hospital setting can decrease clinically significant communication errors and improve clinical outcomes. The aim of this study was to investigate the differences in length of stay (LOS) and 30 day readmission rates associated with provision of PIS in the Emergency Department (ED) and inpatient wards. A retrospective audit at a tertiary referral adult hospital in Brisbane, Australia, identified all admissions of patients requiring an interpreter. Patients provided an interpreter in the Emergency Department had a mean (age-adjusted) LOS 22.4 h less than patients not provided an interpreter in ED (95% CI 10.9–33.9). For patients provided with an interpreter on the ward the mean LOS was longer, (IRR 2.2, 1.8–2.3, p < 0.0001). There was no association between interpreter provision in either ED or the inpatient ward and readmission rate. Provision of PIS in the Emergency Department to those patients who require it can significantly reduce hospital LOS.