Due to the increasing demand for technical textiles, particularly in functional textiles for clothing and home textiles, the future of textile development focus mainly on the investigation and fabrication of functional chemical textile fibres. The Institute for Textile Machinery and Textile High-Performance Materials (ITM) is developing a new functional fibres from Phase Changes Materials (PCM) using the simple and conventional melt spinning method on the standard industrial melt spinning machine. PCM has originally been considered as one of the most effective thermal energy storage system for buildings. Recently, we have successfully incorporated the innovative PCM pellets in the form of textile fibre yarns with core-and sheath cross sections, in which the sheath is made from different thermoplastic polymers (TPs), such as Polypropylene (PP), Polyethylene Terephthalate (PET) and the core is a mixing of PCM with these respective TPs. The incorporation of PCM in the core provides a potential for preparing an important functional feature of textile fibres: thermo-regulated smart textiles. By changing the core/sheath volume ratio as well as the blend ratio of PCM with thermoplastic polymers in the core, the storage energy of the fibres can be well controlled. The thermal capacities of PCM incorporated in filaments were determined using the difference scanning calorimetry (DSC). By considering the relationship between the thermo-exchange, textile-physical properties and the morphology of core/sheath filaments, the spinning conditions were optimized.