OBJECTIVES:  Information on adherence among diabetes patient is rare in Bayelsa State, Niger Delta. The objective of the study was to determine the rate of adherence to therapy among diabetes mellitus patients. METHODS:  It was a cross sectional survey with the use of an interviewer-administered questionnaire. A 4-item Morisky self-reported adherence scale in addition to other self-developed, validated and pretested questionnaires were used. This was administered to 263 patients receiving treatment at the Outpatient Department of the hospital after seeking and obtaining their consent between June and August 2012 on clinic days. Questions related to demographics, medication history, adherence rate, etc., were included. In addition, the respective case notes (263) of the same set of patients were examined, and relevant data extracted (such as blood glucose level). Data was appropriately analysed using SPSS. Descriptive statistics were used in presentation of results. RESULTS: Majority of the 210 patients (80.0%) were taking both metformin and glibenclamide tablets. About 60 percent, 156 (59.3%), of patients were adjudged adherent with prescribed medications on the 4-item Morisky scale of adherence with a score of 1.22±0.2, which differs significantly from the non-adherent group with a score of 3.34±0.87. (p<0.0001). However, overall adherences to all aspects of diabetes management were poorer as only 80 (30.5%) had normal fasting blood glucose level of less than 6.1mmol/l after at least five visits to the hospital. Only 42 (16.0%) patients self monitor their glucose level. The most frequently reported factor affecting adherence is high cost of drug therapy, 118 (44.8%), and forgetfulness, 99 (37.6%). Most of the patients, 201 (76.4%), have developed one complication or the other such as hypertension and glaucoma. CONCLUSIONS:  There is poor adherence to anti-diabetic therapy among the patients. Financial constraint was found to be the most important factor affecting optimal adherence to therapy.