Martes martes and Martes foina are the only two Italian species of the genus Martes. As they are very similar in morphology and coloration, their taxonomic identification may represent a hard task. We aimed to assess the reliability of baculum length as a diagnostic tool for Italian martens. A sample of 53 adult males belonging to the genus Martes was collected. The identification of individuals as pine- or stone marten followed a 2-step procedure: i) morphometric analysis and ii) cross-checking with genetic analysis. According to the diagnostic ranges of baculum length reported in the available literature, 21 individuals were classified as stone marten and 15 as pine marten, while 17 specimens remained unidentified. Using a “Baculum Index”, defined as: (Head Length + Body Length) / Total Baculum Length, the sample was split into two distinct groups: 21 individuals fell into the 6.24-8.10 range and 32 fell into the 9.52-11.17 range. Genetic analysis led to the same results. While baculum length is insufficient to identify Italian marten species with certainty, the Baculum Index showed to be a reliable diagnostic tool.