ABSTRACT: Low back pain is the most common cause of referral to a physical therapist and is one of the leading causes of disability. Water exercise takes advantage of the unique properties of water that serve to decrease pain while working out. However, Although therapeutic aquatic exercise is mentioned in a number of recent low back pain guidelines, there is no systematic review available looking at the effects of this treatment form .Therefore, this study examined the acute effects of aquatic exercise on pain, and postural control in women with low back pain. The subjects of this study were 28 female patients who had low back pain aged 47 ± 6.9 years old. Using Oswestry questionnaire, the quantity of back pain was evaluated. Their balance control was evaluated by Romberg test. Then the subjects were divided into Experimental and Control groups randomly. The aquatic exercise program was performed by Experimental group three times per week, for 12 weeks; each session was 60 min long. The evaluations were performed before and after the treatment sessions. The control groups did not participate in any training program. Descriptive analysis, independent t-test and paired T-test were used for statistical analysis. After water exercise program the ability of patients in controlling of balance on one leg open eyes (right P= 0.004,left p= 0.001), one leg close eyes (right P=0.02) were significantly improved. Although controlling of balance on one leg (left) close eyes was improved, it was not significantly(p=0.2). Pain was reduced (P=0.001). Aquatic exercise appears to be a safe and effective treatment modality for patients who are suffering from low back pain. It allows those with low back pain to participate in this crucial way of staying healthy.