Abstract <p>Wastewater emanating from industrial, agricultural, and domestic sectors presents formidable environmental challenges due to their substantial pollutant load. Biochar produced through biomass pyrolysis is distinguished by its extensive surface area (100 to 500 m²/g), heightened porosity (57–79%), and superior adsorption capacity, enabling it to effectively capture a diverse array of contaminants such as carbon-based compounds, heavyweight metal ions, and emerging contaminants. These qualities make biochar the best fit for incorporation into hydrogel matrices, renowned for their exceptional swelling, water retention, and biocompatibility. The hydrogel component provides a three-dimensional framework that ensures uniform dispersion and stabilization of biochar particles while allowing controlled release and sustained interaction with the contaminants, thereby reducing the composite material’s overall efficacy in effluent remediation. This review paper is the first that meticulously dissects the multifaceted performance of biochar–hydrogel composites encompassing toxicity assessments and regeneration capabilities. It delves into the synthesis of composites for wastewater treatment, highlighting the unique properties of biochar and hydrogel. The study thoroughly examines the physiochemical properties and synergistic benefits of these composites, alongside the characterization methodologies for kinetics, isotherm models, and adsorption thermodynamics. Also, it explores the composite’s efficacy in eradicating various pollutants, including chromophoric substances, heavy metals, pharmaceutical residues, cyanobacterial toxins, etc., while affirming its biocompatibility and sustainable usage through regeneration studies. Additionally, the amalgamation of AI-driven innovation facilitates simultaneous temporal framework monitoring and optimization of the composite’s performance introducing an advanced methodology for effluent treatment.</p> Graphical abstract <p></p>