While evidence suggests the significant role played by personality traits in affecting the usage of inappropriate and unethical negotiation strategies, studies have rarely examined the dark core. Considering, negotiation frequently involves choosing between economic outcomes and relational gains, this research primarily examines the effect of dark core and the mediating role of relational interdependent self-construal (RISC) in affecting the usage of inappropriate negotiation strategies (SINS), at the person level (Study – 1) (n = 283, managers, India). Further, it evaluates the individual and interactive effect of dark core with two situation level variables, namely, Interdependence and Incentives in a dictator game design (Study – 2) (n = 221, business school postgraduates, India). It was observed that, while at the person level, the effects of dark core were significantly mediated by RISC, at the situational level, the increasing degree of interdependence with the actor and the additional economic incentives offered, significantly interacted with dark core to predict the endorsement of a variety of inappropriate negotiation strategies. In summary, the study examines the role of dark core, clarifies its self – interested nature, propensity for favouring economic gains at the cost of deteriorated relationships and highlights the role of two important situational elements in negotiation.