Objectives: Recent studies indicate that diabetes mellitus, may especially be associated with psychiatric morbidity. Moreover, certain symptoms may occur in both diabetes and psychiatric disorder. This necessitates the development of effective methods for identifying psychiatric disorder among diabetic patients. The aim of this study is to investigate the validity of the Arabic version of the 12-item General Health Questionnaire (GHQ-12) as a screening instrument for psychiatric morbidity among Type II diabetic patients and to define the best cut-off point. Methods: The study was carried out in a primary health care center, in Al-Ain, United Arab Emirates. A randomly selected sample (n=3D71) of non-hypertensive, Type II diabetic, United Arab Emirate nationals, aged 31-73 years who were not suffering from any other chronic medical illness was studied. Study subjects were interviewed by a primary health care physician, who assisted them to complete a ciodemographic questionnaire and the Arabic version of the GHQ-12. Then, all subjects were interviewed by a psychiatrist using the Clinical Interview Schedule. Identified cases were assigned 10th version of International Classification of Diseases (ICD-10) diagnoses. Correlation's were explored using Biserial, Kendall's tau and Spearman rank correlation. The validity of the instrument was tested by performing the diagnostic measures of sensitivity and specificity. The stepwise regression analysis was performed to find out the best predictors for a psychiatric case. Discriminate functional analysis was used to assess the discriminatory powers of GHQ-12. Results: Using the simple Likert scoring method (0,1,2,3), the best cut-off point of the GHQ-12, that balances between sensitivity and specificity was 11/12 with a sensitivity of 81.4% and specificity of 77.8%. The total discriminatory power of the GHQ-12 was 82%, and it was found to have a significant concurrent validity. Questions 2,4 and 6 proved to be the best predictors for psychiatric disorder. Conclusions: The Arabic version of the GHQ-12 proved to be a valid instrument for detecting non-psychotic psychiatric disorders among type II diabetic patients in primary health care settings.