Carnivore reintroductions are assumed to provide numerous ecological benefits, including conservation of the reintroduced carnivores, regulation of prey species and restoration of ecosystems. Reviews of mammalian carnivore reintroductions and resultant ecosystem effects have focused on large carnivores. We reviewed global terrestrial carnivore reintroductions across all taxa including taxonomic bias, prey impacts and their ecosystem effects. We obtained data from 536 conservation translocations across 54 species of terrestrial mammalian carnivore species (Order Carnivora and Family Dasyuridae). A third of all conservation translocations occurred in South Africa and a third within fenced reserves. Small carnivore conservation translocations were generally under-represented compared to large carnivores. Effects on resident prey species or ecosystems from carnivore conservation translocations were rarely investigated. Challenges to ongoing translocations of mammalian carnivores include perceived threats to resident threatened prey species and difficulties in monitoring the ecological effects of carnivore reintroduction. Poor post-release monitoring and a lack of empirical studies remains a persistent problem, contributing to the poor understanding of ecosystem effects following carnivore reintroductions. In addition, we provide a case study into the investigation of prey impacts and ecosystem effects following the reintroduction of a native predator, the western quoll (Dasyurus geoffroii), to a fenced reserve in South Australia. We present an overview of results of investigating prey behaviour changes, trophic cascades and prey impacts after this carnivore reintroduction. As predator reintroduction programs become more common, measuring the dynamic impacts on prey populations and ecosystem effects is increasingly important and our work provides a detailed novel case study.