The confident use of Fabric Reinforced Cementitious Matrix (FRCM) composites in structural rehabilitation is, to some extent, limited by the lack of knowledge on their durability. Certification guidelines require tests on aged specimens, and the scientific literature is continuously growing, but more research is still needed to develop a deeper understanding on the long-term behaviour of mortar-based systems, especially when comprising fabrics (e.g., glass and basalt) that are highly sensitive to alkali attack, because of the alkalinity of inorganic matrices. This paper presents an experimental study on an FRCM system consisting of a bidirectional glass mesh embedded in a fibre-reinforced lime-based mortar. Direct tensile tests were conducted on bare textile specimens and on FRCM coupon specimens after accelerated aging in 0.16% wt Ca(OH)2 aqueous solution, at either 23 ℃ or 40 ℃ temperature, for durations ranging from 1000 to 9000 h. Test results showed that the mechanical behaviour of the glass FRCM system tested in the laboratory is affected by exposure to alkali attack and that the temperature plays a key role in deterioration mechanisms.