OBJECTIVE The study aims to investigate a case of fusion of the permanent central and lateral right maxillary incisors observed in a middle-aged male from the late medieval town of Sisak in Croatia. METHODS "Double teeth" is a term for a developmental anomaly caused by congenital, inherited, acquired and/or idiopathic factors resulting in the union of two adjacent teeth. It usually occurs in three different varieties: concrescence, gemination and fusion. Although there are many reports of such disorders in recent populations, similar examples in archaeological contexts are still rare and, in most cases, recorded in primary dentition. We employed a combination of morphological (macroscopic) and state-of-the-art radiographic analysis (micro-CT scanning). RESULTS The teeth in question are fused in both coronal and radicular pulp parts, indicating a complete fusion in comparison to the left maxillary incisors that have a normal morphology and are completely separated. The fused RI1 and RI2 have a single crown with a slight groove running along the lingual side of the root which is also visible on the buccal side of the root. Two small protrusions (tuberculum dentale) are visible on the lingual side of the crown. Micro-CT scans confirmed that the fused teeth have a single pulp chamber and root canal. CONCLUSIONS The presented case is unique as it is the first known archaeological specimen of permanent maxillary incisors fusion from Europe and one of the very few known cases of the fusion of permanent teeth from archaeological contexts globally.