This study examines the effects of a prescribed fire, conducted in grassland in order to maintain a fire break, on soil quality (pH and nutrients) in the Prades Mountains in the Mediterranean climate of north-east Spain. Soil at a 4 × 18 m study plot, located in an abandoned agricultural terrace on calcareous bedrock at 760 m above sea level, was sampled at 0–5 cm depth at 42 sampling points before, immediately after and one year after the burn and analysed for pH and carbon, nitrogen, potassium and phosphorous content. Fire intensity was low and surface soil temperatures did not exceed 200°C. All parameters examined showed a significant increase immediately after the fire. One year later, pH and total carbon had returned to pre-fire levels, and nitrogen and phosphorous were above, whereas potassium levels had decreased to below pre-fire levels. Overall, the prescribed fire did not appear to adversely affect soil. However, using prescribed burning on an annual basis as a tool to maintain an effective fire break may not allow enough time for the soils to fully recover.