Industry engagement in pre-college STEM programs extends from grants to informal (out of school time) activities including industry involvement by mentoring. Despite these well-meaning investments, present metrics seem to demonstrate slow progress towards positive demographic changes in STEM fields, especially for disenfranchised populations. The objective of this paper is to examine STEM programs supported by industry partnerships within precollege informal STEM environments. This paper uses a systematized literature review to evaluate 121 peer-reviewed articles published in the last thirty years about mentoring in pre-college informal STEM programs. In this review, we identified themes related to mentoring models, increasing gateways to career participation, and increased awareness because of the participation of industry mentors. The findings provide recommendations for implementing and supporting mentoring initiatives with industry partners in pre-college informal STEM settings. Future work may include how partnerships with industry can support mentoring in informal STEM programming for pre-college students.