Studies on the association between sitting time and low back pain (LBP) have found contrasting results. This may be due to the lack of objectively measured sitting time or because socioeconomic confounders were not considered in the analysis. To investigate the association between objectively measured sitting time (daily total, and occupational and leisure-time periods) and LBP among blue-collar workers. Two-hundred-and-one blue-collar workers wore two accelerometers (GT3X+ Actigraph) for up to four consecutive working days to obtain objective measures of sitting time, estimated via Acti4 software. Workers reported their LBP intensity the past month on a scale from 0 (no pain) to 9 (worst imaginable pain) and were categorized into either low (≤ 5) or high (> 5) LBP intensity groups. In the multivariate-adjusted binary logistic regression analysis, total sitting time, and occupational and leisure-time sitting were both modeled as continuous (hours/day) and categorical variables (i.e. low, moderate and high sitting time). The multivariate logistic regression analysis showed a significant positive association between total sitting time (per hour) and high LBP intensity (odds ratio; OR = 1.43, 95%CI = 1.15-1.77, P = 0.01). Similar results were obtained for leisure-time sitting (OR = 1.45, 95%CI = 1.10-1.91, P = 0.01), and a similar but non-significant trend was obtained for occupational sitting time (OR = 1.34, 95%CI 0.99-1.82, P = 0.06). In the analysis on categorized sitting time, high sitting time was positively associated with high LBP for total (OR = 3.31, 95%CI = 1.18-9.28, P = 0.03), leisure (OR = 5.31, 95%CI = 1.57-17.90, P = 0.01), and occupational (OR = 3.26, 95%CI = 0.89-11.98, P = 0.08) periods, referencing those with low sitting time. Sitting time is positively associated with LBP intensity among blue-collar workers. Future studies using a prospective design with objective measures of sitting time are recommended.