Core leadership and employee performance have long been a clich and permeate every industry, and interest in the field is growing in both business and academic circles. While numerous scholars have deepened and revolutionized leadership theory through empirical research, a systematic review of these studies has not yet received attention. Therefore, the purpose of this paper is to connect its theoretical development to business practice and to identify directions for leadership development by answering the question of whether and how leadership affects employee performance. In order to explore this topic, this paper used a literature research approach to review and analyze the relevant literature. The major categories of this literature and the main structure of this review consist of four sections: leadership style, leadership behavior, leadership development, and the relationship between leadership traits and employee performance. The analysis shows that scholars generally acknowledge their decisive role in employee performance and that effective leaders need, at a minimum, intelligence, personal charisma, the ability to balance people and tasks, mentoring skills, cross-cultural awareness, the ability to switch styles of dealing with different situations, a sense of continuous self-improvement, and a global mindset.