The cyanotoxins, which are potentially harmful to the health of humans and animals, are toxins produced by cyanobacteria. They can be found in reservoirs used for water supply, especially due to the degradation of sanitary conditions within the watersheds. Therefore, it is essential to assure potable water for human consumption in its distribution. The use of granular activated carbon (GAC) has been studied for advanced water treatment and cyanotoxins' removal. The efficiency of such technology depends on activated carbon intrinsic characteristics and operating conditions. Removing such toxins through biodegration by microrganisms is another possibility. The present study was perfomed in laboratory conditions and analyzed microcystin removal by adsorption by three commercial GACs (source materials: coconut shell, mineral and bone) and through the biological degradation by two genera of bacteria. An extract of toxin was produced by the cultivation of Microcystis aeruginosa (strain BB005), in medium WC throughout 30 days, with a 12 h photoperiod. The activated carbon samples were characterized regarding the apparent density, moisture, pH, ash content, iodine number, methylene blue index and specific surface area. Thereafter, adsorption experiments were conducted with microcystin (initial concentration of 100 μg.L-1) for estimating isotherms considering an equilibrium time of 1 h. The toxin analyses were performed by the ELISA (Enzyme-Linked Immunosorbent Assay) and the data were adjusted to the mathematical models of Langmuir and Freundlich. The best adsorption results were obtained with the mineral carbon (removal percentages of 98%), which also showed the highest values for the iodine number (710 mgI 2 .g-1), methylene blue index (169 mL.g-1), specific surface area (911 m 2 .g-1) and percentage of micropores (70%), with best adjustment of the isotherm through the Freundlich model (R 2 = 0.88). The biodegradation tests of microcystin with Sphingomonas sp. and Brevundimonas sp. were carried out with the sterile and non-sterile toxin (initial concentration of 75 μg.L-1). The results showed that these bacteria were not able to promote degradation of the toxin when it was sterilized. However, the degradation was observed in those tests in which the toxin was not sterilized (reduction up to 98%), suggesting the presence of a microrganism and/or an enzyme responsible for this process, since the cultivation of the strain for obtaining the extract was not performed under sterile conditions. As for future research, it is recommendedthe identification of the factor responsible for the biodegradation of the microcystin, as well as the study of the use of the activated carbon from mineral source in a larger scale (fixed-bed filter). This would help to reach a scale closer to the real water treatment plants and evaluate the biofilm formation in the carbon bed, allowing the comparison of the performance of both adsorption and biodegradation processes in the removal of the target pollutant.