The functionalisation functionalization of biochar-based materials for different applications has been one of the most effective sustainable practices nowadays. Reusing waste to create biochar materials is one of the focal interests of researchers for creating biochar with unique structures and properties produced from different and industrial waste materials. To further enhance these properties, the biochar materials are combined with magnetic materials to fabricate a magnetic-biochar composite that merges the high magnetisation and the abundance of functional chemical groups. Thus, magnetic biochar composites showed great efficiencies in water remediation applications such as the removal of highly toxic organic and inorganic pollutants from aqueous solutions with easy separation and recycling processes. They are also applied in supercapacitors and batteries development as they exhibit good electrochemical properties for energy storage. This chapter presents a comprehensive overview of the latest research on magnetic biochar composites in terms of synthesis routes, properties and characterization techniques, and their applications in environmental remediation and energy storage.