This review summarizes 59 studies on the biological treatment of oil and gas produced water, highlighting its potential for reuse and recycling. Biological treatment, though less commonly used than physical-chemical methods, is gaining interest due to regulatory changes and the need for sustainable water management. The studies show that biological treatment can effectively reduce chemical oxygen demand (COD) in produced water, with average removal rates of 73% when total dissolved solids (TDS) are below 50,000 mg/L and 54% when TDS exceeds 50,000 mg/L. However, salinity can inhibit treatment efficiency, with lower removal rates at higher TDS levels. Fixed-film reactors were the most common treatment method, followed by membrane bioreactors (MBRs). Wetlands and ponds, activated sludge, and anaerobic treatment were also used. Bio-electrochemical systems showed promising results, with high COD removal rates. The review also highlights the importance of pretreatment, nutrient addition, and microbial acclimation for effective biological treatment. While biological treatment is effective for low-salinity produced water, it may not be sufficient for high-salinity conditions. Overall, biological treatment is a viable option for produced water treatment, especially when integrated with other technologies for further contaminant removal. The study emphasizes the need for further research to optimize biological treatment for different produced water conditions.This review summarizes 59 studies on the biological treatment of oil and gas produced water, highlighting its potential for reuse and recycling. Biological treatment, though less commonly used than physical-chemical methods, is gaining interest due to regulatory changes and the need for sustainable water management. The studies show that biological treatment can effectively reduce chemical oxygen demand (COD) in produced water, with average removal rates of 73% when total dissolved solids (TDS) are below 50,000 mg/L and 54% when TDS exceeds 50,000 mg/L. However, salinity can inhibit treatment efficiency, with lower removal rates at higher TDS levels. Fixed-film reactors were the most common treatment method, followed by membrane bioreactors (MBRs). Wetlands and ponds, activated sludge, and anaerobic treatment were also used. Bio-electrochemical systems showed promising results, with high COD removal rates. The review also highlights the importance of pretreatment, nutrient addition, and microbial acclimation for effective biological treatment. While biological treatment is effective for low-salinity produced water, it may not be sufficient for high-salinity conditions. Overall, biological treatment is a viable option for produced water treatment, especially when integrated with other technologies for further contaminant removal. The study emphasizes the need for further research to optimize biological treatment for different produced water conditions.