This project is on Level of competencies possessed by secondary school teachers in teaching biology and its impacts on students academic achievement. The findings showed that there is a significant relationship between teachers’ competence and students’ academic performance in Biology. This might be due to the fact that the intellectual competence of the teacher is a primary asset in the quality of learning the students acquire in schools. A Biology teacher competent in his work, possessing the qualities which enable him to inspire and develop the latent capacities of his students would automatically contribute immensely to the high academic performance of the students in chemistry. Also, teachers’ competence in terms of resourcefulness, effective teaching skills and good evaluation enhance students’ performance. This is in line with the finding of (Ivowi, 2016) that there is a significant relationship between teachers’ competence and students’ performance. This is also in agreement with the findings of (Inyang, 2017), that teaching is effective when the teacher makes use of instructional materials. The results also showed that there is a significant difference between the performance of biology students taught by qualified teachers and those taught by unqualified teachers. This might be due to the fact that a qualified teacher can translate knowledge, skills, attitudes and values in accordance with certain professional principles. A qualified teacher has a good classroom control, effective communication skills, adequate knowledge of the subject and can utilize varieties of teaching strategies in order to enhance students’ performance. (This is in line with the work of (James, 2011) that all teachers need breadth and depth in the subject they will teach, including the understanding of the new knowledge and this calls for high professional qualification).