The purpose of this study is to explore the relationship between employee’s psychological capital, organizational commitment and job performance in Vietnam. In this study, psychological capital and overall organizational commitment are considered as two secondorder constructs. Psychological capital includes four different components: self-efficacy, optimism, hope and resiliency. Organizational commitment comprises three different components: affective commitment, continuance commitment and normative commitment. The study uses the combination of quantitative research method and qualitative research method. Qualitative research method (based on the experts’ opinions) is used to design the official questionnaire, while relationship between concepts is estimated by quantitative research method, which is inclusive of the methods of descriptive statistics, Cronbach’s Alpha, EFA, CFA and CB-SEM. The survey is conducted in two ways: face-to-face and via email. Data are collected from 848 employees across provinces and cities in Vietnam. The findings show that psychological capital and job performance have a positive relationship, organizational commitment has positive influence on job performance, and psychological capital is also related to organizational commitment. All relationship between psychological capital, organizational commitment and job performance of employee are statistically significant. In addition, organizational commitment also plays the mediating role in the positive relationship between psychological capital and employee’s performance.