Only a few studies have tested various effects of negative affectivity (NA) within the job stress process as a whole. The aim of this study is to discover the four potential effects (direct, inflation, mediation, and moderation effects) of NA in the job stressor-strain relationship. In this study, NA, role insufficiency as the stressor, and various strains (psychological and physical symptoms, job satisfaction, organizational commitment, intention to quit, and subjective performance) were measured by the Job Stress Battery. The participants were 160 employees from various sectors and organizations in Turkey. The results indicated that in stressor-strain relationships NA had two distinct effects (direct and mediation), and the type of the effect varied depending on the strain. Implications and future directions for research are discussed in the article.