Biology is a teaching and learning subject at secondary school level in Kenyan schools. Biology plays a key role in industrialization and other sectors of the economy. Biology is a practical subject, which equips students with concepts and skills that are useful in solving the day-to day problems of life. The study of biology aims at providing the learner with the necessary knowledge with which to control or change the environment for the benefit of an individual, family or community. However, the secondary school students’ performance in biology as a learning subject in the Kenya Certificate of Secondary Education (KCSE) in Bungoma District has been quite low over the years. The public outcry and concern by parents, teachers, educationists and students about poor performance in science subjects and mathematics in national examinations is a clear indication that factors influencing student’s performance in these subjects need urgent investigation. The aim of this study was to investigate the influence of teacher related factors on performance of secondary school students in biology. The Cross-sectional descriptive research design and the Ex post facto were employed in this study. Nine (9) secondary schools were randomly selected for study out of 139 schools in Bungoma district. Different categories of schools were used depending on the school set-up and these were (i) Single- gender boys boarding schools (ii) Single- gender girls boarding schools (iii) Single- gender girls day schools (iv) Co-educational boarding schools (v) Co-educational day schools (vi) Co-educational boarding / day schools. A total of three hundred and sixty (360) form three students were randomly selected for the study. A student questionnaire (SQ) and a teacher questionnaire (TQ) were used as the main instruments for data collection. Class mark lists were used as tracking records of performance in biology. Data collected were analyzed using descriptive statistics. The study established that boys perform better than girls in biology. Female teachers were found to have a higher level of science anxiety in the teaching of biology compared to the male teachers. It was established that most teachers still used the traditional lecture method in the teaching of biology and only a smaller percentage were using the new approaches. This study was expected to significantly contribute in the provision of information that could be used by teachers, parents, educationists and policy makers to improve on the teaching, learning and performance of students in biology.