Weeverfish are widely distributed venomous fish that inhabit shallow sandy waters ranging from Norway to Morocco and extending to the Black Sea. Despite the painful sting produced by their venom, we report the first indication of grey seals apparently specialising on this venomous prey. Weeverfish occurred in high numbers within 4% of seal scat samples (n = 149) collected between 2011 and 2013, from Wexford in southeast Ireland. The low frequency but relatively high abundance of weeverfish within the diet samples suggest that some grey seals may have developed a mechanism for specialisation through learned behaviour and/or acquired immunity to weeverfish toxins. The findings highlight potential for investigation into seal foraging behaviour and the mechanisms of venom avoidance.