Territorial fragility reflects the combined impact of demographic, environmental, socio-economic, and structural constraints that limit a region's capacity to adapt and develop. Mountain areas are particularly exposed to such vulnerabilities, often intensified by climate change and functional pressures like tourism. While tourism is typically seen as an economic asset, in fragile contexts it can act as a destabilising force, amplifying spatial imbalances and resource stress.This study proposes an extension of the Italian Municipal Fragility Index (IFC) by adding tourism pressure as an additional indicator. Rather than treating tourism as an external sustainability concern, the approach integrates it as a structural component of vulnerability. The method is tested in the Aosta Valley, a mountainous region with ronounced internal diversity and strong tourism dependency. The empirical findings highlight the extended IFC's ability to capture both persistent and emerging patterns of territorial fragility, improve temporal stability in classification, and reveal functionally (driven vulnerabilities - particularly in tourism - intensive municipalities) otherwise underrepresented in standard assessments.