Among sources of an organization, human resource is regarded as the most important one. Therefore, factors affecting to employees' job performances have to be studied, especially in private clinics, since employees working in these clinics are persons directly taking care of patients. This empirical study will discuss about the Quality of Work Life with characteristics of Working environment (WKE); Facilities (FAC); Promotion policies (PMP); Leadership style (LDS) which are proposed to affect positively to Employee Job Performance (EJP). In addition, the study collected 202 good samples in the private clinics in Ho Chi Minh City to analyze this issue. After analyzing the data and the results showed that, factor affecting most and strongly to EJP was factor LDS with β = 0.330; the second factor affecting positively and strongly to EJP was FAC with β = 0.230; the third factor affecting strongly to EJP was PMP with β = 0.195 and the final one was WKE with 0.166. Besides, basing on this finding, the author suggested managers of private clinics as well as scholars refer this study to orient their strategies or use it as database to improve employees' performance in the internationalized context in the new era and the severe competition between enterprises.