Abstract: Due to the petrochemical energy and environmental challenges, clean and renewable energy sources have attracted the extensive attention. Furthermore, composite phase change materials with high photothermal conversion and thermal energy storage efficiency have received increasing attention. However, their poor heat transfer performance and unsatisfactory heat storage capacity limit their widespread application. In this study, we present a novel approach that utilizes polyaniline (PANI) aerogels as the structural framework, polyethylene glycol 4000 (PEG4000) as the phase change material, and silver nanowires (AgNWs) as thermally conductive fillers. The synthesis involved a low-temperature oxidative polymerization and vacuum impregnation, resulting in well-defined phase change composite materials labeled PEG4000@Ag/PANI. Their structure and performance were characterized using scanning electron microscopy (SEM), Fourier-transform infrared (FT-IR) spectroscopy, X-ray diffraction (XRD), thermogravimetric (TG) analysis, and differential scanning calorimetry (DSC). The high porosity of the aerogel and the capillary and hydrogen bonding interactions between PEG4000 and the framework allow the matrix material to achieve a high energy storage density. The maximum loading of the phase change composite can reach 94.17%. The melting and solidification enthalpies of the phase change composite are 165.17 and 152.77 J·g⁻¹, respectively. Furthermore, the incorporation of AgNWs in the PANI aerogel facilitates heat conduction, resulting in enhanced thermal conductivity; the maximum thermal conductivity is 0.45 W·m⁻¹·K⁻¹, which is 80% higher than that of pure PEG4000. With the excellent light absorption ability of AgNWs and PANI, the photothermal conversion efficiency of the prepared phase change composite reached an impressive 90.61%. To study the effect of AgNWs content on the properties of the prepared composite phase change materials, the composite phase change materials with various AgNWs content were analyzed and characterized. The results reveal that changing the AgNWs content has no effect on the physical properties of the composite phase change materials. However, increasing the AgNWs content increased the thermal conductivity and photothermal conversion efficiency of the composite phase change materials, which is attributed to the high thermal conductivity and excellent light absorption capacity of AgNWs. As a one-dimensional thermal conductive filler with a high aspect ratio, AgNWs have high thermal conductivity, providing a new thermal conduction path for heat transfer. Simultaneously, AgNWs exhibit a plasma resonance effect. The preparation of shape-stabilized composite phase change materials with high energy storage density, photothermal conversion capacity, and thermal conductivity provides new ideas for synthesizing novel composite phase change materials and new materials for light–heat conversion and solar energy storage.