In this study, a paraffin/diatomite composite phase change material (PCM) was used as fine aggregate in the production of novel thermal energy storage engineered cementitious composites (TES-ECCs) featuring high tensile ductility and heat storage capacity. The mechanical properties, volume stability and thermal properties of the developed TES-ECCs were investigated and compared with those of a normal fiber-reinforced cementitious composite (FRCC). It was shown that the TES-ECCs offer much better ductile performance and lower compressive strength, first-crack flexural strength and first-crack stress than the normal FRCC, which used silica sand instead as fine aggregate. The strain hardening capacity of the TES-ECCs is as high as 3.65%. Moreover, the TES-ECCs have noticeably lower thermal conductivity and higher specific heat capacity and afford better overall thermal insulation performance than the normal FRCC. In addition, fly ash was found to improve the TES-ECCs' ductility, decrease their thermal conductivity and drying shrinkage. (C) 2014 Elsevier Ltd. All rights reserved.