Access to post-secondary education in low- and lower middle- income countries (LMICs) is very low. In this paper, we systematically review academic research and grey literature published between 2012-2022 to 1) lay out the state of the evidence on the transitions of students from secondary to post-secondary education in LMICs, 2) describe factors that enable or constrain these transitions, 3) aggregate the effects of programs and policies that have successfully improved student admission and enrollment in post-secondary education, and 4) propose a conceptual framework to guide future empirical work, emphasizing the need for a global research agenda on the topic.