The aim of the present study was to examine associations between the presence of diabetes mellitus and health-related quality of life (HRQOL) among older adults. Using data from 37,054 adults aged 50 years or older who participated in the 2001 BRFSS, we examined the independent association between diabetes and four measures of HRQOL developed by the U.S. Centers for Disease Control and Prevention. Multivariate logistic regression was used to obtain adjusted odds ratios (ORs) and 95% confidence intervals (CIs). On average, older adults with diabetes reported nearly twice as many unhealthy days (physical or mental) as those without the condition (mean: 10.1 [S.E.: 0.32] versus 5.7 [0.43]) after age adjustment. The proportion of older adults reporting 14 or more unhealthy days (physical or mental) was significantly higher among those with diabetes (n = 4032; 11%) compared to those without the condition (OR: 1.64; 95% CI: 1.20, 2.23) after multivariate adjustment. Among older diabetic adults, the adjusted relative odds of having 14 or more unhealthy days (physical or mental) was 1.71 (95% CI: 1.31, 2.22) times greater for those treated with insulin compared to those not treated with insulin. Diabetes is independently associated with lower levels of HRQOL among older adults. These results reinforce the importance of preventing diabetes and its complications through health education messages stressing a balanced diet and increased physical activity.