The g-C3N4-agar hybrid aerogel was obtained by a heating-cooling polymerization process with agar and g-C3N4 powder as the raw material, which showed outstanding adsorption properties due to its three-dimensional network structure. Under the synergistic effect of adsorption and photocatalytic degradation, the hybrid aerogels could effectively remove organic pollutants from wastewater. The g-C3N4-agar hybrid aerogels could adsorb the methylene blue molecules to the surface of the photocatalyst, but the adsorption capacity decreases with the decrease of agar content. In addition, the optical absorption and photocurrent response show remarkable improvement with respect to g-C3N4 -agar hybrid aerogels as compared with that of bare g-C3N4 photocatalyst. The optimized 60% g-C3N4-agar sample exhibited preferable simulated-sunlight photocatalytic degradation efficiency towards the dye and antibiotic pollutants, as well as excellent recycle performance. Such a g-C3N4 -agar hybrid aerogel could be envisaged to possess great potentials in practical wastewater treatment.