Describing young people who offend or who are more likely to offend as vulnerable or having vulnerability seems commonplace in the literature as of late. Although the use of vulnerability in the research literature on youth crime appears widespread, its meaning, nonetheless, is unclear: if not assumed or implicit, it fluctuates across studies. Because of this ambiguity, we systematically review the empirical literature on youth crime between 1990 to 2020 to gauge how vulnerability is understood now and over time. A total of 19 studies out of 631 original records met the inclusion criteria. The included studies neatly fit into pre-existing classifications of vulnerability from the research literature. The vast majority of the included studies appeared in the decade 2010 to 2019, and meanings of vulnerability as social disadvantage and risk first appeared during this time. Overall and underlying meanings of vulnerability as well as their research and real-world implications are discussed.