PURPOSE: There is paucity of information about quality of life (QOL) studies among patients with arthritis and diabetes mellitus in developing countries. The objective of this study was to evaluate quality of life of patients with arthritis (AR) and diabetes mellitus (DM). METHODS: A total of 507 subjects comprising 364 healthy adult volunteers and 143 hospitals patients with arthritis and diabetes mellitus were enrolled into the study. Data were collected using Ferrans and Powers QOL index (QLI). The generic version and disease specific versions were administered to healthy subjects and hospital patients respectively and the data analyzed. RESULTS: The highest mean overall QOL scores of the healthy subjects (364; 71.79%) which ranged from 24.43(SD=4.08) to 26.62 (SD=2.15) (95% CI 24.94-27.27) is the second most desirable category of QOL rating relative to the reference standard score of zero to 30 for the worst and best case scenarios respectively. This was distantly followed by patients with diabetes mellitus alone (slightly satisfied) with mean OQOL score of 18.92 (SD=2.59; 95% CI 16.03-19.24). Subjects with AR had lower OQOL than diabetic subjects with mean OQOL scores of 15.98 (SD=2.75; 95% CI 13.15-16.77). The least mean OQOL score (moderately dissatisfied) was recorded for patients with AR co-existing with other chronic illnesses with a mean OQOL scores of 8.92 (SD=3.97; 95%CI 7.36 - 13.4). There was statistically significant difference between the OQOL of healthy subjects and patients with arthritis and diabetes mellitus (p<0.0001). A strong association also exists between OQOL and age, marital status, employment and gender (p<0.05). CONCLUSIONS: Arthritis and diabetes mellitus severely impaired patient QOL. Arthritis has more pronounced effects on QOL either alone or as co-morbid chronic illness. Concerted efforts at stemming the prevalence of these conditions, supportive roles for the elderly and married women as well as cost effective management of these conditions among others must be put in place.