To equip students with 21st-century skills, teachers must have both deep STEM content knowledge and the confidence to implement and teach appropriate STEM content. Many elementary teachers have inadequate STEM background knowledge, low confidence, and STEM self-efficacy for implementing STEM in the classroom; as a result, teachers' classroom practices are affected. The study examined how elementary teachers perceive their ability to implement STEM in the classroom. The STEM Efficacy Survey was sent to a randomized pool of 100 elementary educators, and 18 of them agreed to participate in the study. This instrument was designed to elicit responses related to the teachers' previous background in STEM, their beliefs about their ability to implement STEM, and their actual STEM implementation in the elementary classroom. The results revealed that participants were confident in their understanding of the engineering design process and problem-based learning. However, teachers were unwilling to apply the engineering design process in the classroom. From this research, the researchers concluded that higher levels of training in STEM education may influence how teachers perceive their ability to implement STEM in the classroom. Further research should focus on exploring how STEM training affects teachers' self-efficacy in STEM implementation.