The chemical regeneration process has been extensively applied to reactivate biochar, supporting its reusability and leading to significant operating cost reduction. However, no recent review discusses the effectiveness of biochar chemical regeneration. Thus, this article comprehensively reviews the chemical regeneration of biochar contaminated with organic and inorganic pollutants. Performance of the chemical regeneration depends on adsorption mechanism, functional groups, adsorbent pore structure, and changes in active adsorbent sites. Secondary contamination is one of the challenges facing the sustainable adaptation of the chemical regeneration process in the industry. The paper discusses these challenges and draws a roadmap for future research to support sustainable wastewater treatment by biochar.