Conservation of huemul (Hippocamelus bisulcus), an endangered South American deer, is hindered by a lack of quantitative information on its population dynamics. We conducted a 3-year study in Chilean Patagonia to assess the dynamics of huemul by monitoring known individuals. We fitted 55 deer of all sex–age classes with either radiocollars, radio ear tags, or conventional ear tags, and identified 33 additional deer through natural marks. Kaplan–Meier estimates revealed that annual survival of adult females was high and stable (0.94 ± 0.07 SD), but survival of female fawns was low and variable (0.13 ± 0.18). Predation was the predominant cause of mortality for deer of all age classes. Fertility rates were lower (0.72 ± 0.20) than in other cervids of similar size. Simulations of the finite rate of increase (λ) suggest that the population is currently stable. Sensitivity analysis showed that any decrease in adult female survival would have drastic effects on λ. Consequently, management should maintain high adult survival and improve recruitment. Continued monitoring of individuals is required to provide baseline data for comparison with other populations and to inform recovery strategies of small and fragmented populations.