A shape-stabilized lauric acid-activated carbon composite was prepared using a one-step impregnation method. Activated carbon (AC) was produced from different wood waste (Scots pine (Pi) and poplar (Pop)), and lauric acid (LA) was used as a phase change material (PCM) for thermal energy storage. Wood waste from Scots pine and poplar was activated with phosphoric acid (A) and zinc chloride (S) at 600 °C for 90 min to produce AC. The AC was examined by Brunauer–Emmett–Teller (BET) analysis, and the properties of the LA/AC composites were investigated by Fourier transformation infrared spectroscope (FTIR), X-ray diffractometer (XRD), scanning electronic microscope (SEM), differential scanning calorimetry (DSC), thermal gravimetric analysis (TG), and thermal conductivity. The BET surface area of the produced AC was 1050, 1130, 625 m2/g, and 746 m2/g for PiA, PiS, PopA, PopS, respectively. The porous structure of AC reduced the leaching of LA during phase change. Differential scanning calorimetry (DSC) results showed a latent heat capacity of 29 J/g and a melting temperature of 48.9 °C for the LA/AC composite. The DSC results indicated that the composites exhibited the same phase change characteristics as those of the LA and their latent heats decreased. The TG results indicated that the AC could improve the thermal stability of the composites. Thermal conductivity decreased by 7.48% in PiA-PCM samples but increased by 6.86% in the PopS-PCM by AC.