Objectives: The purpose of this study was to investigate the relationship between daily physical activity (PA) level and low back pain (LBP) in young women. Material and Methods: Two hundred forty three female, desk-job workers aged 20–40 voluntarily participated in the study. The participants were assessed by the use of Oswestry Disability Index for measuring LBP disability and by the use of the short version of the International Physical Activity Questionnaire for PA assessment. The 1-way ANOVA test was used for comparing the mean values according to the physical activity level groups. Correlations between the average LBP disability score and all the other variables were obtained using Pearson’s correlation analysis. The level of statistical significance was p < 0.05. Results: Significant differences were found for LBP disability score between the results of 3 different PA groups (p < 0.05) (low, mode­rate and high PA groups). The correlation between the average LBP disability score and body weight (r = 0.187, p < 0.01), body mass index (r = 0.165, p < 0.01), vigorous MET score (r = 0.247, p < 0.01) and total PA MET score (r = 0.131, p < 0.01) were significant. Conclusions: The main finding of this study is that there is a U-shaped relationship between PA and LBP disability score in young women. A moderate level of daily physical activity and preventing body weight and fat gain should be recommended in young, female desk-job workers in order to prevent and manage low back pain.