Microcystins are a class of toxins that are mainly produced by cyanobacteria and among them, microcystin-leucine arginine (microcystin-LR) is one of the most toxic and harmful of the fresh water toxins causing many accidents and threats to human health. The detection of microcystin-LR in drinking water and environmental water samples is therefore crucial. To date, methods such as high performance liquid chromatography, protein phosphatase inhibition assay, enzyme-linked immunosorbent assay, and Raman spectroscopy have been employed to monitor microcystin-LR levels. Although these techniques are precise and sensitive, they require expensive instrumentation, well-trained personnel and involve time-consuming processes meaning that their application is generally limited to well-resourced and centralized laboratory facilities. Among the emerging microcystin-LR detection methods, biosensors have received great attention because of their remarkable sensitivity, selectivity, and simplicity. In this review, we will discuss the current state-of-the-art microcystin-LR biosensing platforms, and evaluate the advantages and limitations of typical transduction technologies to identify the most efficient detection system for the potentially harmful cyanobacteria.