With the changes in the positive psychology approach in the period after the 2000s, the effects of positive psychology began to be seen in organizational behavior research (Seligman and Csikszentmihalyi, 2000). However, as a result of recent changes in organizations, negative concepts such as dark personality traits have also been widely examined in organizational behavior studies (Jonason et al., 2012). Individuals with dark personality traits may show negative behaviors such as competitiveness, manipulation and using and exploiting other employees in the organization for their interests. Dark personality consists of narcissism, psychopathy and machiavellianism (Harms et al., 2011). Individuals with narcissistic personality traits, which is one of the dark personality traits, establish all the relationships they establish both in their professional and private lives in line with their interests to achieve their goals quickly; they can use their colleagues while fulfilling the tasks they need to do at work and they can attribute success only to themselves (Glad, 2002). Individuals with machiavellian personality traits aim to achieve their main goals in their working lives no matter what (Atinc et al., 2010, p. 513). Machiavellian individuals who want to maintain their power and be on the strong side of the organization try to achieve their goals by using many influence tactics (Yılmaz, 2012, p. 45; Ertekin and Ertekin, 2003, p. 107; O'connor and Morrison, 2001, p. 304). The symptoms of psychopathy, which is the last component of the dark personality, are not feeling remorse for irresponsible behaviors, showing deceitful behaviors and being indifferent to the emotional pain that other people may feel (Aydoğan and Serbest, 2016, p. 103). Individuals who show psychopathy traits are only focused on achieving their goals in their working lives and do not care about the damage they cause to the work environment. Individuals with dark personality traits experience incompatible and difficult relationships with other individuals due to these negative traits which negatively affect the health of the organization. These individuals may show negative work behaviors such as low work performance and job dissatisfaction. Leaders who show dark personality traits can cause an increase in the stress level of other employees and lead to the spread of negative behaviors in the organization. In this book chapter, the emergence of the concept of dark personality (dark triad), its dimensions, reasons, and its importance in terms of working life will be discussed.