The ever-changing complex business environment has created a need for leaders who can meet the demands and challenges of organisations who are grappling with the new organisational climate, with a real need for improved productivity and competitive performance in order to survive. To achieve this target, it is imperative for both leaders and organisations to change their way of thinking to foster and sustain the motivation and satisfaction levels of their employees for maintaining their competitive edge. This research, hence, aims to explore the relationship between leaders’ leadership behaviours and employees’ level of job satisfaction in two petrochemical companies in Libya: Raslanuf Oil and Gas Processing Company (Rasco) and Harouge Oil Operations Company. The relationship between these two variables and the selected demographic characteristics of the employees - namely age, gender, marital status, number of dependents, job grade, job classification, educational qualifications and tenure - were examined. It should be noted that the literature survey indicates that no previous research conducted on the nexus between the leadership behaviour and its impact on the level of job satisfaction of Libya’s petrochemical companies’ employees. This lack of empirical research, hence, was the primary motivator for this study. The study employed Avolio and Bass (1991) full range of leadership theory (transformational, transactional and lassiez-faire) to determine the leadership behaviours in these two companies. In addition, Herzberg’s job satisfaction theory (1959) which is based on the Job Satisfaction Survey (JSS) was utilised to measure the level of job satisfaction of employees in the mentioned companies. Structured questionnaires in the form of the Multifactor Leadership Questionnaire (MLQ) by Bass and Avolio (1995) to measure leadership and the Job Satisfaction Questionnaire (JSS) by Spector (1997) to measure the level of job satisfaction, were employed as the data collection methods. The sampling frame was comprised of 70 of the 340 leaders, and 280 of the 3481 followers at Rasco Company, and 40 of the 120 leaders and 110 of the 1480 followers for Harouge Company. The study generated an 86.12% response rate (96% for Rasco and 76.25% for Harouge) with 451 participants (110 leaders and 354 followers) who worked at these two Companies at the time of the questionnaire administration. The collected data were computed and analysed using descriptive statistics, t-test, analysis of variance (ANOVA), correlation, multiple regression analysis, exploratory factor analysis and multiple discriminant analysis to explore the relationships between these variables in a systematic manner. The research findings indicate a statistically significant relationship between transformational leadership dimensions, especially the two dimensions of individual consideration and intellectual stimulation behaviours, and employees’ job satisfaction levels within the two companies. The findings demonstrate that the leaders tend to be perceived by their employees as demonstrating transactional and laissez-faire leadership behaviour more often than transformational behaviour in the case of the two companies analysed. It should, however, be noted that the exercise of a degree of transformational leadership behaviour by leaders was much lower than employees’ expectations showed. There was also a significant association between the employees’ job satisfaction level (which is significantly higher in Rasco than at Harouge), and operation conditions, nature of work, fringe benefits, supervision and communication. Demographic characteristics are further identified as non contributors to the level of job satisfaction.