This study investigated the effect of pyrolysis temperature and heating rate on the properties of biochar produced from olive mill solid waste (OMSW). Various analyses were carried out, including biochar yield, proximate and ultimate analysis, higher heating value (HHV), pH, point of zero charge (PZC), Fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and BET analysis. These analyses revealed that as the pyrolysis temperature increases, ash and carbon content, fixed carbon, HHV, PZC, surface area, and total pore volume increase. However, an increase in pyrolysis temperature leads to a reduction in both biochar yield and oxygen-containing functional groups. The heating rate showed a positive relationship with the oxygen content, surface area, micropore volume, and total pore volume. In contrast, the heating rate had only a slight effect on the ash content, HHV, and PZC. The maximum values of carbon content and fixed carbon were observed in the biochar produced at a heating rate of 20 °C/min, which indicates improved stability and carbonization. Taken together, these results suggest that selecting the pyrolysis temperature and heating rate should be optimized according to the environmental or agricultural application of biochar to maximize its benefit in these applications.