This paper explores the extent to which Biology syllabi are open to students' engagement with and acquisition of critical thinking skills in Tanzania's developing country context. It focuses on the Biology syllabus of Ordinary-level secondary education and that of Advanced-level secondary education. The paper reports the findings of a study whose primary objective was to explore the coherence of the two syllabi under review with the elements of critical thinking skills drawn from extant literature. The analysis also entailed exploring the coherence between the specific objectives of the syllabi linked with critical thinking skills and the assessment questions suggested. The study used the Atlas TI programme to analyse the data to achieve the research objectives. The findings revealed that the specific objectives in the syllabi under review focus mostly on lower order thinking (LOT) skills, according to Bloom's taxonomy of learning, rather than on higher order or critical thinking skills.