In this study, the researcher investigated the biographical and human resource management (HRM) predictors of union membership. The literature reviewed revealed that there is little research on this topic in the South African context. The literature reviewed also showed that males, permanent employees, employees who are less committed, who have a level of quality of work-life (QWL) and engagement, and those who are satisfied are more likely to be unionized. A cross-sectional survey design was used to address the research questions. One thousand questionnaires were distributed and 874 were completed by the respondents at Marabastad Mall in the City of Tshwane Metropolitan Municipality (CTMM) in South Africa. The study results showed that employment status was the highest predictor ( = -1.782, p<0.05) of union membership, and gender and job satisfaction were not predictors of union members. This study had managerial implications, in the sense that when hiring employees on a part-time basis, having employees who are committed and offering employees QWL (i.e. excellent fringe benefits) will impact negatively on union membership. In terms of policymakers, the study revealed that developing remuneration policies that are pro-employee (i.e. offering excellent working conditions and fringe benefits) would make them satisfied, possibly be productive, and they would engage less in counterproductive industrial actions like strikes, which in South Africa are the amongst highest in the world.