Human-carnivore conflicts and retaliatory killings contribute to carnivore populations’ declines around the world. Strategies to mitigate conflicts have been developed, but their efficacy is rarely assessed in a randomized case-control design. Further, the economic costs prevent the adoption and wide use of conflict mitigation strategies by pastoralists in rural Africa. We examined carnivore [African lion (Panthera leo), leopard (Panthera pardus), spotted hyena (Crocuta crocuta), jackal (Canis mesomelas), and cheetah (Acinonyx jubatus)] raids on fortified (n=45, total 631 monthly visits) and unfortified (traditional, n=45, total 521 monthly visits) livestock enclosures (“bomas”) in northern Tanzania. The study aimed to (i) assess the extent of retaliatory killings of major carnivore species due to livestock depredation, (ii) describe the spatio-temporal characteristics of carnivore raids on livestock enclosures (iii) analyze whether spatial covariates influenced livestock depredation risk in livestock enclosures, and (iv) examine the cost-effectiveness of livestock enclosure fortification. Results suggest that i) majority of boma raids by carnivores were caused by spotted hyenas (nearly 90% of all raids), but retaliatory killings mainly targeted lions, (ii) carnivore raid attempts were rare at individual households (0.081 raid attempts/month in fortified enclosures and 0.102 raid attempts/month in unfortified enclosures), iii) Spotted hyena raid attempts increased in the wet season compared to the dry season, and owners of fortified bomas reported less hyena raid attempts than owners of un-fortified bomas. Landscape and habitat variables tested, did not strongly drive the spatial patterns of spotted hyena raids in livestock bomas. Carnivore raids varied randomly both spatially (village to village) and temporally (year to year). The cost-benefit analysis suggest that investing in boma fortification yielded positive net present values after two to three years. Thus, enclosure fortification is a cost-effective strategy to promote coexistence of carnivores and humans.