Textiles integrated with phase change materials (PCMs) are gaining increasing consideration recently in the textiles market due to their smart thermal performance. PCMs are thermal energy storage materials, when combined in textiles they can sense the changes in the environmental conditions and react to provide the required equilibrium. In this work, four yarn samples were produced from different materials namely; cotton G94, cotton G86, cotton G86/polyester and polyester fibres, and were treated with PCMs composites to acquire theirs with thermoregulation properties. The yarns were treated with Octadecane as PCM loaded on pectin stearate and/or alginate stearate. The thermal and physio-mechanical properties of the yarns were characterized to evaluate their functional performance. The results were statistically analysed using ANOVA at a P ≤ 0.05 significance level. The results revealed that all treated yarns with PCM composites showed smart behaviour with imparting the thermoregulation property; they exhibited higher latent heat and Duration index (DI) compared to the untreated yarns. Also, the yarns coated with pectin/alginate/stearic offered higher latent heat and DI than the yarns coated with pectin/stearic and the yarns coated with alginate/stearic as hosting materials. Moreover, all yarns coated with the PCM composite materials showed preferable results and are arranged as follows; cotton G86/polyester, polyester, cotton G86, and cotton G94. The PCM composite treatments showed a highly significant effect on most of the physical and mechanical properties of yarns, especially polyester and cotton G86/polyester yarns.