Today, about 50% of US elementary schools have a pre-kindergarten (pre-K) program located in the building. This article systematically reviews the empirical literature on principal leadership of pre-K programs in elementary schools. We collected studies using academic database searches, scanning reference lists of relevant articles, and consulting with experts in the field. Our efforts yielded 16 sources for review. Using thematic synthesis, we analyzed the data to reveal key findings related to principal leadership of pre-K programs. There has been limited scholarly attention to principal leadership in the pre-K context. Prominent themes in the existing literature on the topic include (1) a common framing of the "colliding" worlds of pre-K and K-12 education, (2) principals' beliefs about pre-K, (3) the scope of principal responsibility for pre-K programs, and (4) principal preparation to lead pre-K programs. We unearthed limited evidence on the topic but charted a path for future research on pre-K principal leadership. Future research should focus on the design of principal capacity building efforts that have direct, positive impacts for students.