Temporomandibular disorders (TMDs) are associated with pain and dysfunction that can affect the quality of life. This study was designed to evaluate the import of dysfunctional severity on the quality of life in TMD patients. This case-control study involved 60 TMD and 60 non-TMD subjects. The Helkimo dysfunction index was used for classifying the TMD patients into mild, moderate and severe groups (n=20). The quality of life (QoL) was assessed using the World Health Organization Quality of Life-Brief Version Questionnaire (WHOQOL-BREF) in the control and different TMD classifications. The data were analyzed by one-way analysis of variance (ANOVA) and Tukey post hoc test. There was no significant difference in the scores of physical, psychological, social and environmental subscales among the four groups (P>0.05), but a significant between-group difference was noted in the overall subscale (P=0.003). Tukey test revealed that the mean overall subscale score in the severe group (49.37± 18.35) was significantly lower than that of the mild group (66.06± 17.97). Although QoL was lower in moderate and severe TMDs than mild cases and the control group, but the statistical difference between groups was only observed in the overall subscale. These data indicate that other factors than the severity of TMD could play a role in QoL of affected patients.