This paper reports a pilot study to determine the potential impact of an integrated STEM curriculum on Pre-K teachers' engineering content knowledge, self-efficacy and teaching practice. Using a randomized control trial design, researchers examined the impact of the curriculum in 17 Pre-K classrooms (8 intervention classrooms, 9 control classrooms) in central Massachusetts. Questionnaires measuring STEM and engineering content knowledge, self-efficacy and teaching practice were administered to participating Pre-K teachers (N = 42; 21 intervention, 21 control) in Fall 2017 and again in Spring 2018. Baseline analysis showed no significant differences in engineering and STEM content knowledge, pedagogical content knowledge, or teaching self-efficacy at the start of the pilot study between intervention and comparison classroom teachers. Fidelity of implementation was measured using an observation instrument developed by the project team based on a published implementation science framework. We hypothesized that teachers who implement the integrated STEM curriculum will have significantly higher engineering pedagogical content knowledge and self-efficacy than teachers in the comparison group. As well the teachers who implement the integrated STEM curriculum will show significant gains in their engineering pedagogical content knowledge and self-efficacy in teaching engineering and STEM as a result of their participation. [This paper was published in: "2018 IEEE Integrated STEM Conference (ISEC)" p234-237. ISBN 978-1-5386-3309-0. Institute of Electrical and Electronics Engineers.]