The purpose of this paper is to investigate the influence of personality and grit on the Organizational Citizenship Behavior (OCB) of lecturer, and if this relationship is valid whether this relationship is mediated by job involvement or not. A case study research with quantitative approach was used in this study. The sample size consists of 132 of lecturers at the industrial vocational higher education of the ministry of industry in Indonesia were selected by using multi-stage sampling procedure. Data were collected by using questionnaire at a single point in time and analyzed with SEM-PLS. The findings revealed personality and grit were the predictors for the Organizational Citizenship Behavior of lecturers and job involvement mediated partially the causal relationship between personality and grit to OCB, although it was in the indirect effect with enough strength. The finding had contributed for ensuring the position of job involvement as a mediating variable in the relationship between personality and grit on OCB, which in the previous studies were not explicitly placed as a mediating variable.