In this paper, we propose an in-line fiber sensor probe based on UV-glue-assisted cascaded Fabry–Perot cavities for temperature measurement. The UV-curable adhesive in the sensing cavity plays an important role due to its high thermo-optic coefficient. We show that the temperature sensitivity depends on the optical path length difference between both cavities. We report a maximum value of 12.57 nm/°C in the range of 20 to 30 °C. This original sensor architecture features a low cost and simple structure that can be straightforwardly manufactured with readily available materials and a short production time.