The Gough Moorhen is endemic to Gough Island and is classified by the IUCN as Threatened. We present several observations of Gough Moorhens preying on introduced House Mice Mus musculus and on eggs and chicks of burrow-nesting procellariiform seabirds. The incidence of egg predation is almost certainly related to incubation breaks or abandonment. We estimate that Moorhens could access and depredate unattended eggs of at least five species but levels of predation appear to be low and are unlikely to affect population parameters of impacted species. Moorhens hunting live mice and scavenging carcasses presents a significant conservation concern. A possible eradication of mice from Gough Island is likely to employ poisons that are toxic to the Moorhens. Therefore secondary poisoning of Moorhens, by eating poisoned mice, is a threat to the Gough Moorhens. An eradication effort will be required to take appropriate mitigation measures. The introduced Gough Moorhen population on Tristan da Cunha serves as an ex situ population and could, if required, be used to re-stock Gough.