This study sought to find out the extent of use of biology teaching and learning resources and how it affects students’ academic performance. The study was carried out in public secondary schools in Siaya County. The researcher used a sample of twenty-three schools drawn from ninety two public secondary schools selected through stratified random sampling. Teacher respondents were purposively or randomly sampled. Purposive sampling was used to choose the most experienced biology teacher from two or more teachers teaching form two classes. Where there existed more than one long serving and experienced teachers teaching form two classes, random sampling was employed to pick one of them for interview. Student respondents were chosen through random sampling in single sex schools and stratified random sampling in mixed schools. Head teachers from each of the sampled schools were selected for personal interview. The data were collected using questionnaires, checklists, observation schedules and interview guides. Observation schedules were used by the researcher to ascertain use of resources by teachers and learners and the resultant tests used to determine the score differences in achievement between classes frequently taught using resources and those rarely taught using resources. Interviews with head teachers were used to countercheck the information given by teachers and students on utilization of resources. The findings of the study established that audio-visual resources were least used in schools. The resources were mainly bought by the headteachers. The researcher’s assessment during live lesson teaching using observation schedules showed that students frequently taught using resources performed better than those rarely taught using the resources. The research also established that frequent use of resources was not the only factor determining high student’s academic performance but other factors like teacher’s qualification, pedagogy, attitudes and students’ entry behaviour also played a role in realizing improved academic performance in students.