PurposeMental ill health (MIH) is a global concern for employees, particularly in the construction industry. However, there is still a lack of studies that investigate the MIH of construction employees, especially in developing contexts like Vietnam. This study aims to examine (1) the current status of employees' MIH and (2) the effects of employees' awareness of MIH on their MIH, employing the Health Belief Model (HBM) as the theoretical framework.Design/methodology/approachThe review of previous studies enabled the establishment of research hypotheses regarding the relationships between six HBM constructs and MIH. The questionnaire was then developed and distributed to Vietnamese construction employees using snowball sampling. Collected data were analyzed using the Partial Least Squares Structural Equation Modeling (PLS-SEM).FindingsAmong the 238 surveyed participants, 21.8% reported experiencing mild MIH, 62.2% were experiencing moderate levels of MIH, and 15.1% were facing severe MIH. The findings highlighted that respondents who had graduate degrees and management positions reported a higher level of MIH than those with bachelor's degrees and engineer roles, respectively. The findings revealed that perceived severity, perceived benefit, cues to action, and self-efficacy negatively influenced MIH. In contrast, high perceived susceptibility and perceived barriers were associated with increased MIH.Originality/valueThis study emphasizes the alarming situation of Vietnamese construction employees regarding MIH. The findings underscore the importance of targeted strategies based on employee characteristics such as job role, education level, and years of experience. Additionally, it calls for broader societal efforts to raise awareness and create supportive environments for mental wellbeing.