This study sought to investigate the relationship between students’ personality types and their academic achievement in Oromia Colleges of Teachers’ Education. Three Colleges of teacher education, namely: Danbidollo, Fiche and Nekemte were selected by purposive sampling techinqe . The study employed descriptive survey research design. The sample size was 150 female& 201 mal trainers. A questionnaire was used as instruments of collecting data from the students while interview was administered with teachers. Interview, observation and document analysis were used to crystallize the information obtained through questionnaire. Quantitative data analysis was done using descriptive and inferential statistics such as frequency counts, percentages, means, standard deviation, pearson correlation and one way ANOVA test. Results of data analysis were presented using frequency distribution tables. The study established that neuroticism and extroversion were negatively related to academic achievement; conscientiousness, agreeableness and openness have a positive association with academic achievement Among others conscientiousness personality type was a good and strongest individual predictor of academic achievement at the colleges of teachers training. Moreover, neuroticism personality type determines lack of emotional stability that lead to hindrance to academic achievement.The researcher concluded that agreeableness; Conscientiousness and Open to experience personality types were correlated with students’ of high academic achievement. The study, therefore, recommends the skill of teachers and students should be strengthened by training such as seminars or workshop on personality traits and their impact on students’ academic achievement. It’s worthy of attention to try to institutionalize conscientious trait during initial years of education, by presenting appropriate conscientious role models or encouragement of conscientious people. Findings of this study can also emphasize the necessity of informing curriculum developers of the personality traits and individual differences of learners, so as to help them take such differences into account and be more flexible while developing educational curriculums.