This Campbell systematic review examines the predictors of youth gang membership in low‐ and middle‐income countries. The review summarises findings from eight reports from five countries and the Caribbean region. The lack of available evidence limits the extent to which clear conclusions can be drawn about the factors associated with youth gang membership. The review is based on a very small number of studies, and has significant limitations in coverage. The limited evidence of the correlates of youth gang membership suggests factors that may drive gang membership and suggests areas where interventions may prove promising in the family, school, and community domains, as well as provide a starting point for future studies. Plain language summary Evidence shows which factors predict gang membership in low‐ and middle‐income countries, but more studies neededYouth gang membership is associated with delinquency, violent crime and trafficking. A range of individual, peer, family, school and community factors can predict the likelihood of youths getting involved with gangs. Knowledge of these factors can be helpful for reducing gang membership. What is this review about?Youth gang membership is associated with delinquency, violent crime and trafficking – and gang members are themselves frequently the victims of these offences. Yet youth gangs can also provide a form of social capital, a sense of belonging and purpose to disenfranchised youth.This review identifies the factors associated with young people joining gangs, and the differences between gang‐involved and non‐gang‐involved youth. Understanding these associations is essential to reduce the levels of gang membership and the incidence of related violence. What studies are included?Studies of youth gangs in in low‐ and middle‐income countries were included, with participants aged 10‐29 years. The studies had to assess an individual predictor or correlate of youth gang membership, where the predictor or correlate is a single characteristic, not a conglomeration of multiple constructs. Included studies had designs including data on both gang‐involved and non‐gang‐involved youth, recruited with strategies that were eligible.Nine studies met the eligibility criteria and were included in the review. One of these studies did not report all the required data and so was not included in the analyses. The studies were conducted in Turkey, Trinidad and Tobago, the Caribbean, El Salvador, China and Brazil.Factors associated with gang membership Domain Significantly associated with gang membership No significant association with gang membership IndividualDelinquency Alcohol and soft drug use Male gender Risky sexual behaviours Employment Psychological risk factors (low self‐control, impulsivity) and lack of psychological protective factors (empathy, future orientation, belief in moral order) VictimisationAge Minority ethnicity Protective behaviours surrounding sexual behaviour or alcohol and soft drug use.PeerSocialising with delinquent peersSocialising with pro‐social peers...