Diabetes mellitus is a serious public health problem that leads to substantial disease and death rate. Diabetes has resulted into a lot of complications such as renal failure, retinopathy, and heart diseases and is accounted as the 7th leading cause of death worldwide. This study was carried out to determine the knowledge, attitude and practice of adult patient living with type 2 diabetes using data mining approach in Nigeria. The participants from this study were from secondary data obtained from different journals from seven states in Nigeria. Data were collected using data mining approach from numerous set of data to get hidden knowledge. Data was entered using IBM Statistical Package for Social Sciences (SPSS) and was analyzed using both descriptive and Chi-squared automatic Interaction detection (CHAID) analysis. CHAID was used to develop the decision tree model which is used for the prediction of the knowledge, attitude and practice. Result showed that the participants comprised 2070 participants of which 56.8% where female and 43.2% were male. The Socio demographic characteristics have been revealed to have a role in the knowledge, attitude and practice of type 2 diabetic patient in that it is found out that marital status is the major determinant of knowledge in type 2 diabetic patients because about 100% of adult patient with marital status had good knowledge of 89.8%, also education is the major determinant of attitude in type 2 diabetes patients and knowledge is the major determinant of practice in type 2 diabetes patients. The adult patient had good knowledge on type 2 diabetes of 59.5%, poor knowledge of 31.1% and fair knowledge of 9.5%. This study also shows that 47% of diabetes mellitus patient had good attitude. 8.6% had fair attitude, and 44.4% had poor attitude of the ailment. Also, the study also shows that 52.5% of type 2 diabetes mellitus had good practice, 21.9% had fair practice and 25.6% had poor practice. Therefore, this study concluded that majority of the patient had good knowledge of diabetes. Nevertheless, there is a need to educate patient on issues relating to diabetes mellitus and ensure compliance to the interventions needed in the management of type 2 diabetes mellitus.