The literature supporting leadership as the most important factor related to organizational success or failure is burgeoning. To a large extent, this may explain why so much research focuses on factors influencing leadership effectiveness. A crucial aspect of leadership research is to determine why some individuals perform effectively in leadership roles while others demonstrate mediocre or low levels of effectiveness. Once measures of individual characteristics have been validated within a relevant context, they become useful sources of information for selecting, placing, and promoting people into leadership positions. The aim of this study was to determine if there are statistically significant differences in emotional intelligence between effective and ineffective leaders. The sample included 114 leaders at the middle management level in a public sector institution in South Africa. Each leader’s effectiveness was rated by themselves (self-rating), as well as by four subordinates, thus involving 570 participants. The EQ-i® was used as a measure of emotional intelligence, while Spangenberg and Theron’s Leadership Behaviour Inventory was used to determine leadership effectiveness. Multivariate analysis of variance indicated that the effective leaders scored significantly higher on the total emotional intelligence measure. They also scored significantly higher on two emotional intelligence composite scales (Interpersonal EQ and Stress Management EQ) and six sub-scales (Self-actualization, Empathy, Social Responsibility, Stress Tolerance, Problem-solving, and Optimism)