In an increasingly fast-changing world of organizational leadership, emotional intelligence (EI) has become a major determinant of effective leadership. Historically, technical skills and cognitive intelligence have dominated the leadership development paradigm, but empirical evidence is growing that EI training can enhance leadership competencies, team dynamics and organizational outcomes. Using a mixed-methods approach, this research paper critically examines the impact of emotional intelligence training on leadership development by means of a thorough literature review, analysis of a recent large-scale secondary dataset from Kaggle and advanced statistical techniques. Study examines how EI training impacts leadership effectiveness, the contextual moderators (organizational culture and industry) that impact the effectiveness of the training and ways to best incorporate EI into leadership development programs. Results show that EI training results in statistically and practically significant increases in self-awareness, self-regulation, empathy and social skills, which in turn produce improved leadership performance, team cohesion and employee satisfaction. Recommendations for practitioners and future researchers are provided in the paper, highlighting the need for culturally sensitive and evidence-based EI interventions in leadership development which are personalized. Keywords: Leadership Development, Emotional Intelligence, Empirical Research, Organisational Behaviour, Team Performance, Employee Satisfaction, EI Training, Leadership Effectiveness