Nature-based Solutions (NbS) have the potential to tackle both the biodiversity and climate crisis, while supporting ecosystem services such as climate mitigation, water regulation, and natural hazard control like landslides and avalanches. However, it often remains unclear whether NbS focusing on improving carbon capture or protection against hazards are still effective in biodiversity conservation. On a global scale, about two thirds of NbS-cases aiming at climate change mitigation also reported positive effects on biodiversity, but a research gap exists specifically for mountain areas. Since mountain ecosystems are highly sensitive to global change pressures, such as climate and land-use change, here, knowledge on NbS outcomes is urgently needed to guide decision-making and planning. Therefore, we performed a systematic review evaluating the effectiveness of NbS in conserving and improving biodiversity in mountain areas across the world, while excluding NbS focusing on pure conservation and restoration actions. We analyzed the NbS with respect to different typologies of NbS, bioclimatic belts, land cover types and uses, as well as different aspects of biodiversity and related indicators. Our findings contribute to knowledge on which factors play a key-role of NbS in maintaining biodiversity in mountain areas and support policymakers in developing and implementing effective NbS.