The aim of this study was to examine the levels of health-related quality of life (HRQoL), pain intensity, and mental distress in participants with chronic low back pain (CLBP), and to examine the differences in the HRQoL of participants with respect to mental distress and the correlations of the examined variables. Data were collected from 148 patients using the SF-36 Health Status Questionnaire (SF-36), the Clinical Outcomes in Routine Evaluation-Outcome Measure (CORE-OM) questionnaire, and the visual-analog pain scale (VAS). The results indicate poorer self-assessment of physical health (M = 28.1) compared to mental health (M = 39.4). Participants with higher levels of mental distress reported significant emotional limitations ( = 0.003), lower energy ( < 0.001), poorer psychological health ( < 0.001) and social functioning ( < 0.001), more pain ( = 0.007), and, ultimately, poorer general health ( < 0.001). The level of mental distress was related to the level of HRQoL, while a correlation with the level of pain of the participants was not found. The study results indicate a connection between the presence of mental distress and almost all aspects of HRQoL in participants with CLBP.