Meta-analytic studies have consistently reported that job performance has a significant relationship with personality traits. However, only a limited number of researches have been conducted to find the mechanisms that mediate this relationship. Thus, this study attempts to examine the direct role of personality traits as predictors of job performance and the indirect influence of achievement motivation as a mediating variable. Personality measurement tools are adapted from Cattell and achievement motivation from Cassidy and Lynn. Job performance indicator is obtained from annual job performance evaluations. All three personality traits are integrated into a model that predicts job performance and achievement motivation. The model is tested using structural equation modelling (SEM) with a sample of 450 public administrative officers. Results of the model show that it has goodness of fit and achievement motivation is found to fully mediate the relationship between conscientiousness and agreeableness toward job performance. However, emotional stability directly influences job performance. All the predictors contribute 24% of the variance in job performance. Implication of the finding is that emotional stability and achievement motivation can be the essential predictors in predicting job performance of future candidates followed by agreeableness and conscientiousness.