The purpose of this research is to develop an understanding of the factors that support or constrain the individual's sharing knowledge in the organization. The current study seeks to explore whether personality (self-efficacy and self-esteem) and situational (cognitive appraisal: threat versus challenge) characteristics influence participants' knowledge sharing in the organization. The research was conducted during the summer semester of the 2009 academic year and encompassed two main groups of Israeli librarians: academic librarians and public librarians. The study used five questionnaires: a personal details questionnaire, perceptions towards knowledge management questionnaire, a cognitive appraisal questionnaire measuring threat versus challenge, a self-efficacy questionnaire, and a self-esteem questionnaire. The results show that personality and situational characteristics influence participants' knowledge sharing in the organization. The findings may have theoretical as well as practical implications.