Purpose: This study was performed to investigate the convergent validity, discriminative validity, and reliability of the Brazilian version of the low anterior resection syndrome (LARS) score in a population with low educational and socioeconomic levels. Methods: The LARS score was translated into the Portuguese language by forward- and back-translation procedures. In total, 127 patients from a public hospital in Brazil completed the questionnaires. The convergent validity was tested by comparing the LARS score with the European Organization for Research and Treatment of Cancer (EORTC) Quality of Life Questionnaire Core Module 30 (QLQ-C30) and with patients’ self-reported quality of life. For the discriminative validity, we tested the ability of the score to differentiate among subgroups of patients regarding neoadjuvant radiotherapy, type of surgery, and tumor distance from the anal verge. The test-retest reliability was investigated in a subgroup of 36 patients who responded to the survey twice in 2 weeks. Results: The LARS score demonstrated a strong correlation with 5 of 6 items from the EORTC QLQ-C30 (P<0.05) and good concordance with patients’ self-reported quality of life (95.3%), confirming the convergent validity. The score was able to discriminate between subgroups of patients with different clinical characteristics related to LARS (P<0.001). The agreement between the test and retest showed that 86.1% of the patients remained in the same LARS category, and there was no significant difference between the LARS score numerical values (P=0.80), indicating good reliability overall. Conclusion The Brazilian version of the LARS score is a valid and reliable instrument to assess postoperative bowel function in a population with low educational and socioeconomic levels.