The Next Generation Science Standards emphasizes the inclusion of engineering practices throughout the K-12 science curriculum. Therefore, elementary educators need to be knowledgeable about engineering and engineering careers so that they can expose their students to engineering. The purpose of this study was to examine the effect of engineering professional development on in-service elementary teachers': (a) knowledge and perceptions regarding engineering, and (b) self-efficacy of teaching engineering. This quantitative study revealed that even one professional development opportunity can help to alleviate some misconceptions about the work of engineers and what constitutes technology, as well as increase teachers' confidence to teach engineering concepts.