AbstractSince they arises in many stages of manufacturing as well as at the end of their lifetime, glass fiber reinforced polymers‐based wastes are one of the biggest problem for the composite industry. There are many waste disposal methods available, but these are low value‐added and usually imply additional cost to the manufacturers. In this study, composite wastes have been ground into three different grain sizes and used as filler in the production of new glass fiber reinforced composites. Composites were examined regarding their rheological, thermal, mechanical, dynamic‐mechanical, and morphological properties. High thixotropy a resin could be obtained by waste incorporation ensuring easier gel‐coat application in hand lay‐up molding technique. A remarkable reduction in linear shrinkage of the resulting composite was also considered as a benefit. Although there was tolerable loss in their mechanical properties, higher grain size of waste particles shifted glass transition temperature up to 50°C higher due to restricted chain mobility. Fibers from both the waste matrix and fresh glass fiber content exhibited quite similar interphase with the unsaturated polyester. In summary, using composite waste in their own composition has been found to be a good solution to recover the wastes in both economic and environmental concern.