HMS Brocklesby identified and recovered five dummy sea mines in a minehunting operation around the Strait of Gibraltar.
The Portsmouth-based vessel worked with 20 other warships from 17 Nato countries in a training exercise designed to test how a task group keeps sea lanes free in disputed waters.
The exercise, run by Spanish forces, was co-ordinated by Maritime Component Command based at Northwood in the UK.
Brocklesby discovered five dummy mines in her area of operations, which was the most recovered by any ship during the exercise.
The Royal Navy Hunt Class mine countermeasures vessel left Portsmouth at the end of January for a six-month deployment to the Mediterranean.