Arsenic (As) is a toxic metalloid that is distributed globally. It has two oxidation states, trivalent As and pentavalent As. As(III) is more toxic than As(V). As is mostly released into the environment by natural sources and man-made causes. It is the most significant environmental pollutant due to human activities. According to the World Health Organization (WHO) report, the presence of a high concentration of As in drinking water is the leading cause of serious health problems and the WHO recommends a maximum concentration of As(10 μg/L) in drinking water. It is incredibly difficult to remove As from the environment. There are various methods for removing As from contaminated soil and water. The effectiveness and waste associated with each method depend on criteria such as speciation, starting adsorbate concentration, absorbent types, and interfering species. As removal from the environment may be done efficiently and sustainably via biological methods. Microorganisms remove As from water, soil and sediments by metabolism, detoxification, oxidation–reduction, bioadsorption, bioprecipitation, and volatilization processes. The most effective approach to cleaning up polluted areas may require the use of hybrid (biological, chemical, and physical) and best-available technologies (BAT). This chapter focuses on the biological removal of As from the environment.