The use of low-cost and ecofriendly adsorbent was investigated as an ideal alternative to the current expensive methods of removing dyes from wastewater. In this study, activated carbon from olive-tree wood was used as an adsorbent for the removal of Congo red dye from aqueous solutions. Acidic and basic functional groups and surface structure of the obtained activated carbon were analyzed by Bohem titration, pH of point of zero charge (pH_PZC) and scanning electron microscopy (SEM). Langmuir and Freundlich adsorption models were employed to provide a description of the equilibrium isotherm. Furthermore, the pseudo-first-order and pseudo-second-order kinetic models were used to study the mechanism of dye adsorption by the activated carbon. The thermodynamic studies indicated that the adsorption of Murexide occurs in a spontaneous and exothermic process. The fitness of the Langmuir model to the adsorption process points that the Congo red dye was adsorbed on specific monolayer onto activated carbon. According to the obtained findings, activated carbon, produced by the chemical activation of olive waste wood, could be used as an effective and low-cost adsorbent to decrease the concentrations of dyes in wastewater. The results of this research highlight the importance of recycling agricultural waste to decrease environmental contamination and conserve natural resources. This encourages researchers to conduct further investigations in this area.