Science, Technology, Engineering, and Math (STEM) and Computer Science (CS) are the driving forces of the United States prosperity. While there is a high demand to close the gap in STEM+CS jobs, there is little research in K-12, especially in K-5 level. Elementary teachers lack of self-confidence in STEM+CS and there is limited number of teacher training. Here, Integrating Computational Thinking (CT) in elementary science classrooms comes into prominence. International Society for Technology in Education (ISTE), Computer Science Teachers Association (CSTA), and Next Generation Science Standards (NGSS) emphasize that CT learning is an important part of the elementary curriculum. It can be translated that elementary teachers should have the self-efficacy, interest, and confidence to integrate CT into their teaching. It is not an easy task to expect such a demand from pre-service elementary science teachers (PST) unless necessary training is provided. It leads us to modify our elementary science teaching methods course to integrate CT to improve PST' CT self-efficacy beliefs, interest, and confidence in elementary teaching. The goal of our research is to investigate the changes in PST' CT teaching efficacy beliefs, interest, and confidence after participating in CT training as part of an undergraduate elementary science teaching methods course. We have found that our course improved PST' CT teaching self-efficacy beliefs, interest, and coding confidence.