To inform trapping protocols to reduce by-catch while trapping feral cats by-catch welfare costs should be quantified. During cat trapping programs at six Western Australian sites from 1997-2015, 431 non-target individuals, including 232 individuals from native species (132 mammals, 52 birds and 42 reptiles) were captured. Among the native fauna; birds were more likely to be severely injured (33%, compared to 12% in mammals and 21% in reptiles). Amongst other vertebrates, larger individuals were less likely to be injured. Olfactory lures used in these studies attracted reptiles, but repelled mammals. By-catch varied with climate and landscape. Trap injury to by-catch species poses ethical concerns, especially for threatened species that can least afford an additional threat. Future trapping should consider the timing of trapping, trap placement, trap settings (especially the treadle pressure needed to close the trap) and new innovations sending immediate capture alerts to minimise by-catch and potential injury associated with prolonged restraint. By-catch welfare data should be analysed to identify best practice and on-going improvement.