Critical thinking as a 21st-century skill is needed by students to anticipate today's global changes and is very relevant to the implementation of the elementary school curriculum in Indonesia. This research discusses the implementation of the scientific approach to improving elementary school students' critical thinking skills. This research aimed to explain the concept of critical thinking, scientific approach, and development of critical thinking skills through the scientific approach in elementary school students' learning. This study used a qualitative approach with a literature review. Data were obtained from various references related to the research topic. The data analysis technique used is the Miles & Huberman technique which includes data reduction, data display, and conclusion drawing/verification. The research reveals that (a) critical thinking involves skills and dispositions in thinking; (b) the scientific approach in the 2013 curriculum involves observing, asking questions, gathering information, associating, and communicating; and (c) the average score of students' critical thinking engaged in the scientific approach-based learning is higher than the score of students engaged in the conventional learning. Accordingly, the scientific approach can improve students' critical thinking skills in elementary school. Based on these findings, it is recommended that elementary school teachers implement the scientific approach in the learning process to improve elementary school students' critical thinking skills.