Abstract: Phase change materials (PCM) has been increasingly used over the past decades to combat the large amount of energy needed for thermal comfort of human beings. Organic PCM is desired in temperature control, but it suffers from thermal leaking and unstable form during phase transition. This study aimed to develop cellulose nanofibrils (CNF) – phase change mamterials based functional materials for thermal management applications. PCM, using paraffin as an example, is encapsulated into micron-sized emulsions using CNF as interfacial stabilizer. We expected that microencapsulation using CNF can improve the flexibility and thermal stability of PCM, and such emulsion can be used in various applications such as spray coating and 3D printing. Firstly, CNF/PCM Pickering emulsion can be stabilized due to the amphiphilic nature and strong network of CNF with optimized sonication conditions, including sonication time and amplitude, ratio of CNF and PCM, and CNF.