The efficiency of a Sequencing Batch Biofilm Reactor (SBBR) for domestic wastewater treatment in Basrah was assessed. The experiments were carried out via a laboratory-scale SBBR cylindrical vessel used for this study, with geometric volume of 26 L, having an internal diameter of 15 cm, a height of 40 cm, and a working volume of 13 L. After a one-month start-up cycle for biofilm growth on the fibrous filler, the SBBR research test period lasted two months. The SBBR was run for three weeks to ensure that the biological treatment systems were mature and those steady-state requirements were reached, throughout the starting-up phase of operation, the removal efficiency for COD, NH 3 -N, TN, and TP were 95%, 89%, 85%, and 93% respectively. The impact of aeration time on the SBBR efficiency was also tested by removal of COD, ammonia, total nitrogen TN, and total phosphorous TP under different levels of dissolved oxygen DO (2.0 -6.8) mg\L. The SBBR method proved to be an effective method for treating domestic wastewater in Basrah city.