Low back pain (LBP) is a major public health issue. There is lack of research on this disorder affecting urban cleaning workers. A cross-sectional study was conducted to describe the prevalence of LBP, occupational and extra-occupational characteristics, as well as associated factors in these workers. A census was performed with 624 workers in Salvador, Brazil, using a questionnaire administered by an interviewer in 2010. Cases of LBP were defined by reported symptoms of pain in the previous 12 months, lasting more than a week or with monthly minimum frequency, which led to restrictions at work or to seeking medical attention, or in cases when respondents had a severity score ≥ 3 on a numerical scale from 0 to 5. Physical demands at work were measured on a numerical 6-point scale with 14 variables. Psychosocial demands were measured using the Job Content Questionnaire. Sociodemographic factors, lifestyle habits and domestic work were evaluated. Multiple logistic regression (LR) was used to identify factors associated with LBP, for which the prevalence was 37.0%. Among them, 62.8% of workers felt pain in the last 7 days. LBP was associated with longer working hours, flexion and trunk rotation, psychosocial demands, working directly in collection and low schooling. Dynamic work (walking, running) served as a protective factor. It was concluded that many workers develop their activity at the presence of pain. The results emphasize the need for preventive measures through multifactorial approach encompassing adaptations in physical environment and changes in work organization.