ABSTRACT Objective: To analyze the influence of multimorbidity on the treatment outcome of new cases of pulmonary tuberculosis. Method: A population-based analytical study, using secondary data, collected from the database of the Notification Disease Information System, of new cases of pulmonary tuberculosis in the state of Rio Grande do Sul between 2013 and 2016. The relationship between multimorbidity and the outcome was analyzed with Multinomial Logistic Regression. Results: Multimorbidity was present in 37.0% of the cases. Of these, the Relative Risk (RR) was 1.7 for treatment abandonment and 2.9 for death. HIV had an RR of 2.1 for dropout and of 3.9 for death. The higher the number of comorbidities, the higher the RR for unfavorable outcomes. Conclusion: Multimorbidity influences on unfavorable outcomes of the treatment for tuberculosis.