The application of phase-change materials (PCMs) for solar energy utilization and thermal energy storage is limited by their low thermal conductivity, undesirable solar-thermal conversion efficiency, and poor shape stability. Here, the novel paraffin/Ti3C2Tx@gelatin (PA/T@G) composite PCMs were successfully obtained by encapsulating paraffin (PA) into gelatin aerogels modified by Ti3C2Tx nanosheets. Three-dimensional (3D) porous gelatin aerogel acted as a favorable supporting material for PA with large enthalpy, while the Ti3C2Tx nanosheets contributed to enhancing the thermal conductivity and converting solar energy into thermal energy by trapping photons and heating molecules. The results exhibited that the composite PCMs had high load rates (96.3-97.7%) and large melting enthalpies (184.7-199.9 J/g). The thermal conductivity of PA/T-30@G was 0.919 W/(m.K), which reached up to 3.48 times that of PA, and the solar-thermal conversion efficiency of the composite PCMs was greatly improved via the introduction of Ti3C2Tx nanosheets. Notably, the composite PCMs with good shape and thermal stability is a promising material for solar-thermal energy storage applications.