This chapter describes Imogene King's Interacting Systems Theory (IST), which posits personal, interpersonal and social systems, in constant and changing interaction, which provide the context for interaction among individuals, relationships, and groups. Identifying emotional intelligence (EI) abilities as an operationalization of the skills King's theory suggests 1. their role in therapeutic relationships 2. their utility in nursing process and 3. their importance as mediators of caring, effective communication, rapport building, and interpersonal relationship skills, which research findings in nursing as well as other disciplines have shown that these abilities correlate with EI. The nursing process depends on EI abilities. It creates strong relationships with patients, fostering trust and effective communication. EI abilities also enable nurses to integrate thinking and feeling to use emotions to reason, improving their clinical reasoning pathways. The nursing process becomes an integrated phenomenon, weaving together thinking, feeling, and care planning.