PurposeCurrently, small and medium-sized enterprises (SMEs) concentrate on developing their employees’ potential to ensure high job performance. Enhancing the perception of efficacy is important to encourage employees to perform their responsibilities with increased self-confidence. Perceived environmental support and knowledge sharing are also significant factors that boost employees’ potential to achieve targets. The purpose of this paper is to examine how self-efficacy (SE) relates both directly and indirectly to employee job performance through perceived environmental support and knowledge sharing.Design/methodology/approachEmpirical data were garnered from a sample of 344 admins working at SMEs in Central Thailand and structural equation modelling was used to test the proposed relationships.FindingsSE had a strong positive influence on employee job performance, perceived environmental support and knowledge sharing, while perceived environmental support and knowledge sharing positively influenced employee job performance. Perceived environmental support and knowledge sharing were considered to be partial mediating factors of SE in the employee job performance model.Originality/valueThis research extends understanding of the relationship between SE and employee job performance. The findings shed light on mediating roles of perceived environmental support and knowledge sharing regarding the relationship between SE and employee job performance.