Thermal variations are currently among the most significant threats to concrete. First, they can increase the stresses to which concrete is subjected. Second, these changes often lead to the appearance of cracks, which hinder concrete’s durability and ability to maintain a prolonged service life by creating pathways for water and other harmful agents to penetrate. Fiber-reinforced concrete (FRC) is commonly used to withstand these issues, as this type of reinforcement helps to maintain the original dimensions of concrete and stitch the cementitious matrix to prevent cracking. Nowadays, researchers have begun to use sustainable fibers to mitigate the high environmental impact of conventional concrete and fiber production, such as the impact of such materials obtained through the mechanical treatment of Wind-Turbine Blade Waste (WTBW). In our research, mixes containing WTBW of up to 10% vol. were manufactured, and their Linear Coefficient of Thermal Expansion (LCTE) was studied using a novel methodology developed by the authors. These specimens were left in an environmental chamber for 6 months in order to achieve shrinkage stabilization, and then they were subjected to temperatures from -30oC up to +80oC in different steps while the thermal strain that they experienced was measured with a comparator (± 0.001 mm). Next, the length variation of each specimen was divided by the original length and the difference in temperature, which allowed the LCTE of that specific mixture to be obtained through a regression methodology. The lower thermal deformability of the components in WTBW, mainly glass fiber-reinforced polymer, yielded enhanced results, with up to 17% strain reductions recorded, and all mixes exhibited values below conventional plain concrete. Additionally, no cracking or visible damage was observed in any specimen, regardless of the WTBW percentage incorporated. Therefore, enhanced thermal behavior of the mixes was achieved while providing a solution for WTBW recycling and increasing concrete sustainability, which facilitated the creation of greener materials.