Small-scale excavations were recently undertaken at the site of Ukunju Cave in the Mafia Archipelago, Tanzania, to collect new bioarchaeological and material culture data relating to the site's occupation and the nature of early subsistence and long-distance trade in the region. Our findings suggest that occupation of the cave began during the Middle Iron Age (MIA, seventh to tenth centuries AD), as indicated by the presence of local Early Tana Tradition (ETT)/Triangular Incised Ware (TIW) pottery in the lowest layers above bedrock, as well as small quantities of imported ceramics and glass beads also dating from the mid- to the late first millennium AD. Small assemblages of faunal and botanical remains, including introduced African crops (pearl millet, sorghum, baobab and possibly cowpea) were found in association with these finds, indicating that these MIA communities practised a mixed economy of fishing, domestic livestock keeping and agriculture. In addition, the presence of cotton suggests they may have also been producing fibres or textiles, most likely for local use, but possibly also for long distance trade. Although some quartz artefacts were recovered, we found no evidence of any pre-Iron Age LSA culture at the cave, contrary to previous claims about the site.