The growing global energy demand and escalating environmental concerns have spurred the development of sustainable energy solutions, including advanced thermal energy storage (TES) materials. Phase Change Materials (PCMs) have gained prominence for their ability to store and release latent heat during phase transitions, enabling passive temperature regulation and energy efficiency in buildings. While paraffin-based PCMs are valued for their thermal performance, their reliance on non-renewable sources and high carbon footprint poses environmental challenges. Green PCMs (G-PCMs), derived from bio-based sources such as fatty acids, esters, and waste biomaterials, present a sustainable and eco-friendly alternative. This review outlines the current progress in G-PCM research, focusing on their classification, encapsulation techniques, thermal stability, and integration into building materials. Key challenges such as phase separation, long-term stability, and scalability are addressed alongside innovative strategies to enhance TES performance. The use of waste biomaterials, including waste cooking oil and non-edible plant oils, is discussed in promoting circular economy practices and sustainable construction. This review also presents seven actionable strategies for integrating G-PCMs into buildings to improve energy efficiency. Optimal thermal comfort is essential for occupant well-being and productivity, directly supporting UN Sustainable Development Goals (SDG 7, SDG 11, and SDG 13). G-PCM-integrated systems can lower indoor temperatures by 4–10 °C and have achieved over 80 % energy savings in warm climates. Simulations and experiments report HVAC energy reductions ranging from 15 % to 85 %. G-PCMs offer a promising pathway for low-carbon thermal management in buildings, supporting the transition toward energy-efficient, climate-resilient, and sustainable built environments. © 2025 Elsevier B.V., All rights reserved.