In a globalized economy, Organizational Effectiveness takes place in a heterogeneous environment. Cross-cultural and managerial problems concurrently influence the performance of enterprises. Thus, Multicultural Management and Organizational Effectiveness, explores key managerial factors; and here, the relationships among them contribute to a deeper and more constructive way of improving the performance of multinational managers. Managers from 1,065 multinational companies in Thailand representing 31 different nationalities participated in the research. Multinational Management between Most Effective and Less Effective multinational enterprises are compared. International leader characteristics and organizational culture determine effective multicultural management styles which finally determine executive motivation. Different dimensions of organizational effectiveness, including return on assets, Most Admired ranking, job satisfaction and personal satisfaction relate to specific aspects of leader characteristics, organizational culture and multicultural management style. Particular organizational cultures influence ROA more than other aspects in organizational management.