The first fossil balanuliths are reported from a Pliocene (3.5 Ma) coquina on Mejillones Peninsula, northern Chile. While balanuliths were recently described for the first time, fossil balanuliths are not that uncommon, but they apparently have been unreported. Recently described living balanuliths form around broken parts of bivalve shells that were encrusted while still attached to the complete shell. Here balanuliths are reported on nuclei of trochid and, to a lesser extent, muricid gastropods.