The Serengeti ecosystem spans an extensive network of protected areas in Tanzania, eastern Africa, and a UNESCO World Heritage Site. It is home to some of the largest animal migrations on the planet. Here, we describe a dataset consisting of the sample counts of three age classes (infant, juvenile and adult) of 13 ungulate and one ostrich species. Sample counts were tallied visually from the ground, or, in some instances, aerial photographs, during a period extending from 1926 to 2018. Observed animals were assigned to age classes based on specific criteria for each species. For nine of the 14 species of this dataset, the number of sampling years is over 30. This resulted in a total of 533 different records of count across age classes. By computing age-class ratios, these data can be used to measure long-term recruitment success at different ages of the tallied species. In particular, the temporal extent of these data allows comparison of patterns to other long-term processes, such as the El Niño-Southern Oscillation (ENSO).