The number of available jobs in environmental science, science, technology, engineering, and math (E-STEM) is growing rapidly. Nonetheless, women and Latinx, Black, and Indigenous people remain underrepresented in these fields. A number of diversity pipeline programs have been established with the goal of attracting and retaining individuals from underrepresented groups in E-STEM professions. This article is a comprehensive literature review of K-12 pipeline programs geared toward participants from underrepresented backgrounds. In particular, this study carefully investigates the characteristics of E-STEM programs that exist for students from underrepresented backgrounds and the techniques used to prepare students for the next stage in the E-STEM pathway. This work reveals gaps in the availability of K-12 E-STEM pipeline programs that practitioners may work to address, including the lack of programs for elementary-aged students, the need for programs that introduce coding as a skill for probing E-STEM disciplines, and the benefit of tailoring objectives to the needs of the underrepresented group.