A deposit of coins was recovered during excavations at Songo Mnara, Tanzania, containing over 300 copper Kilwa-type coins. This is the first deposit or hoard of these coins found in a well defined archaeological context and it therefore offers a unique glimpse into both the typology of these coins and their contemporary uses. The ramifications of the Songo Mnara deposit are discussed. In particular, the deposit is firmly attributable to the end of the fourteenth or very early fifteenth centuries, allowing for some chronological resolution. Coins of the late eleventh- to early twelfth-century sultan Ali ibn al-Hasan show that these types remained in circulation for several hundred years. In addition, the common coin type of Nasir ad-Dunya can now be attributed firmly to the fifteenth and possibly fourteenth centuries by this find. Finally, the paper discusses the burial of the coins in the foundations of a stonehouse and the fact that this likely represented the building of value into the house and an investment in place. Other finds, such as a carnelian necklace found with the coins, testify to the importance of this practice.