Microalgae have received increasing attentions due to its capacity of carbon fixation and serving as feedstock for producing biofuels and other value-added products. Microalgae can be used to remediate wastewater for simultaneously nutrient removal and biomass production, thereby significantly lowering the costs of microalgal feedstock. Recently, converting microalgal biomass biochar is of particular interest since biochar has numerous opportunities in application. In this review, innovative methods developed for microalgae-based wastewater treatment are described. Conventional and novel technologies used for producing biochar from microalgal biomass, such as pyrolysis and hydrothermal approaches, are presented. Future challenges and potential applications of the biochar derived from microalgal biomass collected from wastewater treatment system (e.g., soil amendment or adsorbent) are also discussed.