Practical work can be conducted both in the laboratory and out of the laboratory. The purpose of this study was to find out the effectiveness of using practical work in teaching and learning of Biology. The problem of this study was the continued poor learner performance in Biology. Two objectives guided the study as follows: To find the proportion of teachers using practical work in teaching and learning of Biology in secondary schools in Gucha South Sub County and to determine teacher effectiveness in using practical work in teaching and learning Biology in secondary schools in Gucha south sub-county. The target population was 42 Biology teachers in Gucha south sub-county. Saturated sampling technique was used to select all the 42 teachers in the sub County. Data was collected by use of the Biology Teachers’ Questionnaire and the Biology Teaching Observation Schedule. The data was analyzed by use of both qualitative and quantitative data analysis techniques. The findings reveal that the use of practical work in teaching of Biology is still low. It is also concluded that the use of practical work in the sub-county is less effective; furthermore, most of the Biology practical lessons are content-biased which hinders the effectiveness of the practical activity. The findings of this study may be important to inform the educationists and curriculum developers on the extent of use of practical work in Biology. It will also inform education stakeholders on the effectiveness of using practical work in teaching and learning of Biology in Gucha south sub-county which in turn will provide room for improvement.