Perceived job security (JSP) has emerged as a pivotal factor influencing employee engagement and organizational performance, particularly in labor-intensive sectors such as Bangladesh’s Ready-Made Garment (RMG) industry. This study explores the extent to which employees’ demographic attributes (DAEs) and firm characteristics (FCs) shape JSP of employees in this context. A cross-sectional mixed-methods design was employed in this study. Quantitative data were collected from 432 employees across 40 RMG firms using structured questionnaires and multistage sampling. Hierarchical and multiple regression analyses were conducted to examine the relationships among variables. Additionally, qualitative insights were gathered through key informant interviews and were analyzed thematically. The results indicate that both DAEs and FCs significantly influence employees’ JSP, independently and interactively. Interestingly, some demographic variables exhibited negligible effects, highlighting the need for further investigation into contextual or organizational mediators. These findings provide a more nuanced understanding of job security dynamics in industrial settings. This study offers evidence-based insights to enhance employees’ sustainable JSP, linked to employee engagement in the RMG industry. Improved JSP of employees can reduce employee turnover, foster organizational loyalty, and increase productivity. The insights are particularly valuable for sustaining performance in high-pressure industries such as Bangladesh’s RMG sector. This research addresses a notable gap by empirically analyzing the influence of DAEs and FCs on JSP of employees. It lays the groundwork for strategic workforce management in Bangladesh’s RMG industry and other similar labor-intensive contexts.