There is a growing body of bioarchaeological research on eighteenth and nineteenth century colonial Cape Town, a significant node in the transportation networks of both the Indian and Atlantic oceanic slave trades, attempting to shed light on the lives of enslaved persons. Here, a preliminary archaeological isotopic dietary baseline for the colonial Cape is presented. It is apparent from the data that cattle tended to graze far inland from Cape Town in an arid C 3 -C 4 to purely C 4 biome. Sheep/goats grazed close to the settlement or some distance away in C 3 to C 3 -C 4 biomes. A qualitative comparison of the baseline data to that of enslaved persons at The Cape suggests that this population did not consume large amounts of marine protein as has been concluded in the past. The archaeological baseline data was utilised, in combination with published modern data, to create a quantitative dietary reconstruction of a subset of this population using a Bayesian multi-source diet mixing model (FRUITS). The reconstruction confirms that the Cape’s enslaved did not consume much marine protein but relied predominantly on terrestrial C 3 plant protein.