We reviewed the literature up to March 2016 on the effects of nonmaternal voices on preterm infants’ clinical outcomes. Of the 11 studies that met the inclusion criteria, 10 focused on short‐term outcomes and one looked at long‐term effects. The studies mainly showed that vocal stimuli increased preterm infants’ stability in terms of heart rate, respiratory rate, oxygen saturation and behavioural measures. Improvements in feeding skills were also reported. The methods and the measures used in the studies were heterogeneous, making it difficult to draw reliable conclusions. Conclusion Vocal stimuli increased preterm infants’ stability, but further studies are needed.