With their low density and high porosity, aerogels are widely used as supporting frameworks for phase change materials (PCMs). However, the host-guest solid-liquid phase-change systems often encounter difficulties in optimizing the balance between mechanical properties and thermal energy storage performance, the intrinsic advantages of aerogels not being fully realized. Herein, an aerogel-functionalization-PCM strategy, a completely converse route compared to traditional aerogel-filling-PCM method, toward lightweight, flexible PCM for robust thermal management is developed. As a proof of concept, silica aerogel particles (SAPs) as functional components are added to a polyvinyl alcohol-polyethylene glycol network to produce composite PCMs. The addition of SAP reduces the composite PCM's latent heat by 25% but significantly decreases the heating rate by 190% and enhances thermal insulation by 147%, achieving a 28 °C temperature drop at 80 °C. This work provides a fresh perspective on the design of flexible and thermally robust PCMs and demonstrates the feasibility of enhancing thermal protection under reduced latent heat conditions.