Composites were prepared by graft polymerization of glycidyl methacrylate (GMA) into low-quality Brazilian pinewood. Oven-dried pinewood samples were impregnated with GMA (1.5 wt% of benzoyl peroxide as catalyst), polymerized by heat at 90°C for 10 h, and washed with acetone to leach the unreacted chemicals. The characterization was performed by treatability parameters, scanning electron microscopy images, ATR-IR spectroscopy, TGA, differential scanning calorimetry (DSC), mechanical properties, water uptake and dimensional stability measurements, and decay resistance tests. The main results showed that the conversion of monomers into grafted polymers was high—up to 85%. The graft polymerization was confirmed by reduction (∼15°C lower) in the temperature of the main thermal event via DrTG and DSC. A decrease in OH band and an increase of peaks corresponding to CO and CO bonds in ATR-IR also confirmed the grafting. The hygroscopicity and wetting were reduced ∼10 times, dimensional stability improved about 70%, and mechanical properties improved between 55 and 85% after the graft polymerization. Decay resistance also increased both against brown and white rot fungi. The graft polymerization of glycidyl methacrylate can improve many technological properties of low-quality pinewood. POLYM. COMPOS., 38:597–603, 2017.