The aim was to assess the prevalence of chronic multimorbidity in patients with chronic low back pain or other chronic back disorders (BD). We analyzed data from the population-based cross-sectional European Health Interview Survey (EHIS) performed in the Republic of Croatia 2014-2015 by the Croatian Institute of Public Health. Outcome was the point-prevalence of chronic multimorbidity defined as having ≥2 chronic illnesses out of 14 contained in the EHIS questionnaire, after adjustment for ten sociodemographic, anthropometric and lifestyle confounders. Amoung fourteen targeted illnesses were asthma, allergies, hypertension, urinary incontinence, kidney diseases, coronary heart disease or angina pectoris, neck disorder, arthrosis, chronic obstructive pulmonary disease, diabetes mellitus, myocardial infarction, stroke, depression, and the common category “other”. We analyzed data on 268 participants with BD and 511 without it. Participants with BD had a significantly higher relative risk of any chronic multimorbidity (RRadj=2.12; 95% CI 1.55, 2.99; p<0.001), as well as of non-musculoskeletal chronic multimorbidity (RRadj=2.29; 95% CI 1.70, 3.08; p=0.001) than participants without BD. All chronic comorbidities except for asthma and liver cirrhosis were significantly more prevalent in participants with BD than in participants without BD. In the population with BD, the participants with multimorbidity had three to four times higher odds for unfavorable self-reported health outcomes than the participants with no comorbid conditions, whereas the existence of only one comorbidity was not significantly associated with a worse outcome compared to the population with no comorbidities. In conclusion, the population suffering from BD has a higher prevalence of chronic multimorbidity than the population without BD and this multimorbidity is associated with unfavorable health outcomes.