This study applies the-trait-activation theory to the field of national and international dual-business negotiations. The theory provides that each type of situations holds distinguished situational factors; each activates specific personality trait to shape the person's behavior-pattern within a given situation. Negotiations of all types hold two common situational factors: the negotiation type, and the counterpart's style. Negotiators should adapt their styles to match these situational factors to achieve the highest possible outcome across situations. Adaptability requires careful planning of an attainable negotiation goal for each negotiation type, accurate estimate of the counterpart's style, then applying the appropriate competitive or cooperative style. It is evident that not all negotiators can be adaptable, which reflects the role of personality traits in shaping adaptability. This book explores the personality traits that are keen to negotiation adaptability in a new approach.