Aims: Despite all progress made in understanding and treating metabolic syndrome, the study of its impact on quality of life is still controversial and not well understood. The aim of this study was to test the hypothesis that metabolic syndrome can be associated with a worse quality of life. Methods: A controlled cross-sectional study included individuals with metabolic syndrome, from the sub-analysis of a randomized clinical trial about lifestyle modification and cardiovascular risk factors, as well as individuals with no metabolic syndrome, attended as outpatients in several clinics at a general university hospital in Southern Brazil. Measurements were made in individual interviews and included data collection, laboratory tests, and application of general scales such as Mini-Mental State Examination and Medical Outcomes Study Short Form, General Health Survey (SF-36). Comparisons of quantitative data used the Student's t test, followed by analysis of covariance or multiple linear regression for adjustment, and correlation coefficient. For categorical data, the Chi-square or Fisher's exact test were used. Results: The study included 229 individuals, 118 metabolic syndrome and 111 no metabolic syndrome. In univariate analysis, metabolic syndrome was significantly associated with lower scores in the social functioning (p<0.001) and role emotional (p=0.019) quality of life domains, and with the Mental Component Summary score of the SF-36 (p=0.013). However, after adjustments for confounding factors, especially body mass index, the significance of these associations was lost. The only significant association between metabolic syndrome and quality of life that has remained after the adjustments was with worse QOL in the role emotional domain, but only in men (p=0.049). Conclusions: After adjusting for multiple variables, metabolic syndrome was significantly associated with decreased quality of life scores in men in the role emotional domain.Key woRds: metabolic syndrome X; risk factors; quality of life.RESuMO objetivos: Apesar dos avanços no entendimento e tratamento da síndrome metabólica, o estudo do seu impacto sobre a qualidade de vida é ainda controverso e inconclusivo. O objetivo deste estudo foi testar a hipótese de que a síndrome metabólica estaria associada à piora da qualidade de vida. Métodos: Um estudo transversal controlado incluiu indivíduos com síndrome metabólica, advindos da subanálise de um estudo controlado randomizado sobre modificação de estilo de vida e fatores de risco cardiovascular; e indivíduos sem síndrome metabólica, provenientes de diversos ambulatórios de um hospital geral no sul do Brasil. As medidas foram realizadas em entrevistas individuais, que incluíram coleta de dados demográficos, testes laboratoriais e aplicação do Exame do Estado Mental e o Medical Outcome Study Short Form, General Health Survey (SF-36). Para comparações entre dados quantitativos, foram utilizados teste t de Student, análise de covariância ou regressão linear múltipla para os ajustes dos fatores confu...