The purpose of this study is to identify the Role of Higher Diploma Program in Improving Trained Teachers’ Classroom Teaching Methods and to examine how Higher Diploma Program Training changes HDP Trained Teachers’ Classroom Teaching Methods so as to bring changes in college students’ learning. The method employed in this study is descriptive one because it helps to reveal the current major implementation problems after the training of higher diploma. Among 10 CTE in Oromia, three colleges namely, Nekemte, Jimma and Asela were chosen using purposive sampling. The reason for using purposive sampling technique in determining the sample were to examine the certain improvements and changes of HDP experienced beginners since they trained more teacher educators up to the present time.The sample sizes are fifty- Seven students from each college making up a total of one hundred and seventy –one students out of 5,700 and Sixteen HDP trained teachers from each college making up a total of 48 teachers out of 210 were included using probability sampling since the populations were relatively large. Instruments used for data gathering were questionnaires composed of both open and close ended items were set and administered. To cross-check the validation of information gathered, the researcher used semi-structured interview questions beside with personal observation which was used to compare the opinion of respondents with relevant issues of pre-set questionnaires of students and teachers. The major findings denote that HDP trained teachers were able to talk knowledgeably about the key components of the HDP: active learning methods, students centered learning, continuous assessment, lesson planning, classroom management and time management. The researcher recommends that there were an obligatory program of continuous Professional Development for CTE instructors to include annual workshops to remind them of the latest teaching method, as well as lesson observations by a CPD