Refinery wastewater has been causing environmental pollution with serious adverse health effects and environmental destruction. This study aims at evaluating the capacity of cassava peels and sugarcane bagasse biosorbents in removing heavy metals, and organic pollutants from the oil refinery wastewater. The proximate and minerals composition of the cassava peels (CP) and sugarcane bagasse (SCB) was determined using the method of AOAC. The pH, turbidity, biological oxygen demand (BOD), and chemical oxygen demand (COD) were determined using digital pH meter, turbidity meter, 5-Day BOD test, and colorimetric technique, respectively. The heavy metals, phenol, and total oil and grease (TOG) content was estimated using AAS and colorimetric method of AOAC. Batch adsorption test was conducted using completely mixed batch reactors (CMBR) method. The results showed that CP and SCB contain significant (p < 0.05) amount of ash (5.38 %, 2.15 %), fiber (20.63 %, 3.83 %), carbohydrate (7.87 %, 27.64 %), proteins (1.87 %, 1.42 %), moisture (1.20 %, 14.99 %), and lipids (2.52 %, 4.22 %), respectively. The CP (3.72mg/100g, 5.41mg/100g, 8.1mg/100g, 3.00mg/100g, 6.52mg/100g, and 4.26mg/100g) contain high significant (p < 0.05) amount of sodium, potassium, calcium, iron, zinc, and copper compared with that of the SCB (2.33mg/100g, 2.10 mg/100g, 5.40mg/100g, 1.88mg/100g, 2.09mg/100g, and 2.14mg/100g), respectively. The pH value of the wastewater sample treated with the biosorbents was significantly (p < 0.05) high compared with the pH value of the untreated wastewater sample. At significant (p < 0.05) reduction in turbidity, COD, and BOD was observed in the wastewater sample treated with combination of the biosorbents compared with the untreated wastewater. The wastewater sample treated with combination of the biosorbents demonstrated significant (p < 0.05) decreased in phenol and TOG content compared with the untreated wastewater. The biosorbents exhibited high removal efficiency against cadmium, lead, nickel, and chromium up to 65.70 %, 80.30 %, 52.46 %, and 72.70 %, respectively. The biosorbents displayed a methylene blue and Congo red dye removal efficiency of 85.66 % and 74.23 %, respectively. The R2 value of lead, cadmium, nickel, chromium, methylene blue and congo red dye for Langmuir isotherm model is higher than that for Freundlich isotherm model. Thus, the experimental equilibrium data for heavy metals and the dyes were best fitted to the Langmuir model than the Freundlich model.