This paper reports the results of a comprehensive analytical study implemented to develop deflection prediction methodologies for curvilinear reinforced concrete (RC) members with glass fiber-reinforced polymer (GFRP) reinforcement, focusing on precast concrete tunnel lining (PCTL) segments. The first step involved modifying the procedures for estimating elastic deflection, cracking moment, and cracked moment of inertia, which were then introduced for use with curvilinear members. In the next step, three methodologies of effective moment of inertia, integration of curvature, and integration of curvature considering tension stiffening were developed for curvilinear members. Then, the analytical results were compared to the experimental database, and a novel method was developed for predicting deflection in curvilinear GFRP-RC members. In the third and final step, a procedure was developed to adapt the presented methodologies for use with a tunnel segment under real load and boundary conditions. The results indicate that the proposed method could predict the deflection of curvilinear GFRP-RC members with high accuracy.