The construction sector is responsible for a large proportion of carbon dioxide emissions, energy consumption and use of raw materials. Therefore, the need of operating on the seismic vulnerability of building heritage must be combined with environmental sustainability issues. A solution is to use eco-friendly materials, such as natural fibres, that represent a renewable resource with both low environmental impact and cost. In this perspective, the present research investigates a Hemp-FRCM (Fiber Reinforced Cementitious Matrix) made of a single layer of hemp mesh as seismic-energy reinforcement system of existing masonry walls. The mechanical properties of the reinforcement system are investigated by means of shear tests performed on the mesh attached to two different types of support, namely Neapolitan tuff and solid brick stones. Finally, the environmental impact of the product is evaluated through a Life Cycle Analysis and the achieved results are compared to those obtained on a Glass-FRCM system to assess the ecological benefits derived from using this new generation green product.