This review investigates the modification, optimisation, and characterisation of plant-based natural coagulants applied to water treatment. The disadvantages of plant-based materials hinder their application as alternatives to chemical coagulants, necessitating their modification to alter and enhance their physicochemical properties, making them suitable for application. Modification via microwave-assisted grafting copolymerisation has been found to be the most preferred approach compared to conventional methods. Optimisation of the coagulation process using response surface methodology has been shown to be practical. Different techniques are used in determining the physicochemical properties of plant-based natural coagulants. Some of these techniques have been tabulated, describing the properties each technique is capable of investigating. In conclusion, modification and optimisation of plant-based natural coagulants will result in the production of new materials that are stable and suitable for application as coagulants in water treatment. © 2023 by the authors.