This study aims to identify biology prospective teachers’ critical thinking skills in ecological courses at IKIP Mataram. The survey method was carried out in this study involving 100 student determined using purposive sampling technique. An essay-shaped test instrument consisting of 6 items developed by the researcher and validated by experts was used to obtain data on biology prospective teachers’ critical thinking skills. The results showed the percentage of basic clarification indicators reached 27%, basic grouping 11%, conclusion 8%, further clarification, 7%, and strategy and tactics 5%. Each of these catalysts showed ≥ 30% achievement. These results indicate that students' critical thinking skills are still in the low category so that serious handling is important to do.