Objective.In the workplace, colleague relationship deeply affects employees’ work attitude and behavior, but it is rarely taken seriously. Based on the cognitive-affective personality system theory and social network theory, this study examined the influence of three common workplace haters (negative gossiper, two-faced person, and loafer) on employee well-being and knowledge sharing and explores the moderating effect of organizational social capital. Method.The study used longitudinal design, three-wave, and 409 valid supervisor–employee pairs (233 direct supervisors and 409 employees) from 10 companies in Taiwan to test these hypothetical relationships. Results. The findings of this study showed that: (1) workplace haters negatively affects employee well-being; (2) employee well-being positively affects knowledge sharing; (3) employee well-being mediates the relationship between workplace haters and knowledge sharing; and (4) organizational social capital moderates the relationship between workplace haters and employee well-being. Conclusion. The study has important contributions to the literature on workplace haters, coworker interaction, and social capital. Implications for behavioral researchers and human resource managers are discussed.