Tourism may benefit conservation, but some wildlife viewing practices threaten the sustainability of both business and conservation initiatives. In north-west Namibia, conservation-oriented tourism provides tourists with an opportunity to encounter the critically-endangered black rhinoceros Diceros bicornis on foot. We used 123 tourist-rhinoceros encounters and employed a statistical modeling approach to: (1) identify the characteristics of human-rhinoceros encounters that caused rhinoceros disturbance and displacement; and (2) design rhinoceros-human encounter guidelines that improve sustainability. A model-averaging, information-theoretic approach identified tourist approach distance, viewing time and individual encounter exposure as the most significant predictors of rhinoceros disturbance level. A suite of rhinoceros viewing scenarios were modeled for acceptable disturbance risks, and adopted as a rhinoceros viewing policy. The policy reduced encounter displacements by 80% while maintaining a 95% positive feedback rating from guests. We demonstrate an evidence-based, policy-oriented management approach can help improve tourism's contribution towards the conservation of an endangered species.