This study aims to develop a novel composite Phase Change Material (PCM) using eco-friendly and low-cost components for an application of improving thermal inertia of building envelopes. The Coconut fat recovered from underused feedstocks was selected as a bio-based PCM for its good Thermal Energy Storage (TES) characteristics. This bio-based PCM was incorporated in a composite matrix prepared in the laboratory from natural clay and cellulose fibers. The direct immersion method with no vacuum treatment was followed as a simple incorporation process of the bio-based PCM into its matrix. The results of thermal and physicochemical characterizations show that the prepared composite-PCM has the potential to be used for passive TES in building envelopes in order to enhance their thermal inertia.