The purpose of this research was to investigate the instructional practices of a Science teacher at a secondary school in Educational District Four in St. Lucia. The research attempted to find out the teacher’s perceptions of the teaching of science: the instructional practices of the teaching during science instruction with reference to planning, instruction and assessment: and the teacher’s perceptions of the factors which influence the choice of strategies used in the classroom. The investigation was conducted using a case study design. Via the use of interviews and observational checklists, the researcher gathered data from the participant at the selected secondary school. Findings from the study revealed that the teacher had positive perceptions of the teaching of science although it was not always reflected in her instruction or assessment practices. The teacher indicated that factors such as time pressures, lack of resources, timetabling, teacher skill-set, student demographics and personal issues accounted for the choice of instructional strategies used in the classroom.