The purpose of this study was to assess the physical activity level(PAL) of patients with mechanical low back pain (MLBP) and to determine association between the PAL and demographic variables of the patients. Ninety six patients diagnosed with MLBP attending outpatient clinic of Physiotherapy Department in selected hospitals in Oyo and Osun States of Nigeria participated in the study.Global Physical Activity Questionnaire (GPAQ) was used to assess the PAL while a structured questionnaire was used to assess the demographic data of participants. Descriptive statistic and chi square were used to analyse the data. The result of the study revealed that, incidence of low back pain increases with age. The peak incidence was within 50-59 years and declines as from 70 years above. Physical activity level decreases with increase in age. Greater number of patients (61.5%) were on moderate PAL. There was a significant association between age group and PAL, and occupation is significantly associated with PAL of participants at(p < .05).