Age, region, and year-specific estimates of reproduction are needed for monitoring wildlife populations during periods of ecosystem change.  Population dynamics of Steller sea lions (Eumetopias jubatus) in Southeast Alaska varied regionally (with high population growth and survival in the north versus the south) and annually (with reduced adult female survival observed following a severe marine heatwave event), but reproductive performance is currently unknown.  We used mark-resighting data from 1,006 SSL females marked as pups at age ~3 weeks of age from 1994–1995 and 2001–2005 and resighted from 2002–2019 (to a maximum age of 25) to examine age-, region-, and year-specific reproduction.  In the north versus the south, age of first reproduction was earlier (beginning at age 4 versus age 5, respectively) but annual birth probabilities of parous females were reduced by 0.05.  In an average year pre-heatwave, the proportion of females with pup at the end of the pupping season peaked at ages 12–13 with ~0.60/0.65 (north/south) with pup, ~0.30/0.25 with juvenile, and ~0.10 (both regions) without a dependent.  In both regions, reproductive senescence was gradual after age 12: ~0.40, 0.40, and 0.20 of females were in these reproductive states, respectively, by age 20.  Correcting for neonatal mortality, true birth probabilities at peak ages were 0.66/0.72 (north/south).  No cost of reproduction on female survival was detected, but pup production remained lower (-0.06) after the heatwave event, which if sustained would result in population decline in the south.  Reduced pup production and greater retention of juveniles during periods of poor prey conditions may be an important strategy for Steller sea lions in Southeast Alaska, where fine-tuning reproduction based on nutritional status may improve the lifetime probability of producing pups under good conditions in a variable and less productive environment.