In this study, we investigate the effects of temperature-dependent properties and inclined loading on plane waves in fiber-reinforced visco-thermoelastic solids using a three-phase-lag (3PHL) model. The elastic modulus is expressed as a linear function of reference temperature. The problem was solved numerically by the normal mode analysis, and the obtained numerical results of thermal temperature, displacement, stresses, mass concentration, and chemical potential are plotted and analyzed. The graphs show the variation of these quantities with different values of the inclined load and empirical solid constants in the medium. In particular, the oblique loading was shown to be an important factor influencing the variation of all field quantities, while temperature-dependent properties had a significant impact on their changes. The paper presents a novel unified model that simultaneously accounts for thermal, viscoelastic, and diffusive effects in fiber-reinforced materials. This integrated approach offers a more comprehensive understanding of material behavior compared to traditional models that consider these factors in isolation.