Considering that uncontrolled construction and inappropriate choices of products are elements that consistently contribute to create a non-sustainable city, this work paid special attention to building science aiming at evaluating basalt fibre as a potential material for eco-compatible constructions. The microstructural and physico-mechanical properties of cement-based mortars reinforced with basalt fibres have been investigated through mechanical (compression and bending) as well as water absorption tests of the hardened materials. Two different mortars consisting of cement, the most common material on the construction market, plus siliceous aggregate were characterized using thermogravimetric analysis (TGA). The effect of basalt fibres with different morphologies at different contents on the mechanical behaviour of the resulting mortars was investigated. Fibre reinforced mortars showed an improvement in flexural and compressive strength compared to the neat mortars which was found to depend strongly on the type of matrix and content of fibres. In particular, relatively small fibres enhance the behaviour of mortars indicated for renewal and finishing uses. This can potentially lead to many applications of a natural and quite innovative material in ceramic matrices as a substitute to glass, carbon or polymeric fibres in building science.