Purpose: To evaluate doctors’ adherence to Malaysian Clinical Practice Guideline (CPG) 2009 inestablished diabetic patients with hypertension, dyslipidemia, renal diseases, obesity, and also toassess factors associated with guideline adherence and diabetes mellitus control in Pulau PinangHospital, Malaysia.Method: Prescriptions written by 24 doctors for 480 established diabetic patients with hypertension,dyslipidemia, renal diseases and obesity (20 patients per doctor) were noted. The control of the diseaseand CPG adherence were noted from the selected prescriptions.Results: Three hundred and forty nine (72.7 %) patients received guideline-compliantpharmacotherapy. CPG adherence had statistically non-significant association (p < 0.301) withhypertension, hypertension with dyslipidemia (p < 0.078), dyslipidemia (p < 0.061), renal diseases (p <0.544) and obesity (p < 0.073). Two hundred and ninety nine (62.3 %) patients were at goal bloodglucose level. Diabetes Mellitus (DM) control had statistically significant association (Ф = 0.583, p <0.001) with guideline compliance and statistically non-significant association (p < 0.066) with comorbidities and also non-significant association (p < 0.300) with therapies.Conclusion: Prescribing practices were fairly compliant with guidelines. Doctors poorly adhered toguidelines in diabetic patients with hypertension, dislipidemia, renal diseases and obesity. Significantlybetter diabetic control was seen in patients who were on monotherapy and guidelines-adherent therapy.