Cougar (Puma concolor) kittens are a substantial proportion of resident cougar populations and their survival has important implications for population dynamics of the species. To better understand effects of age and sex on cougar kitten survival, we estimated age specific (mo.) survival rates of cougar kittens (n = 72) radiocollared during three studies conducted in Oregon from 1989–2011. Cougar kittens were entered into the dataset based on age (mo.) at capture and fates were determined at monthly intervals. We analyzed survival in Program MARK using known-fate models of radiocollared individuals. We tested for effects of sex and linear, log-linear, and quadratic effects of age. Our best model indicated survival rates of cougar kittens were similar between sexes and increased in a linear manner with age. Annual survival estimates of cougar kittens were 0.66 (95% CI = 0.42–0.84). Our second ranked model was the null model, that indicated constant survival over time and between sexes with an annual survival rate of 0.78 (95% CI = 0.62–0.88). All other models in our candidate model set were not considered further because they ranked below the null model and contained non-informative parameters where the estimated effect broadly overlapped zero. Fates of littermates were dependent due to high levels of mortality at nursery sites which likely reduced the potential importance of sex on survival rates. We expect patterns of increased kitten survival with age and lack of differences between sexes to be consistent across the geographic range of cougars.