Multinational corporations (MNCs) are enterprises which have operations in more than one country. They manage production establishments or deliver services in at least two countries. MNCs conduct a significant proportion of their operation in other countries. Therefore, they can have influence on other countries economic entire environment. The controversies whether MNCs help or harm development especially of developing countries have been examined in this paper. To attain this purpose, a brief definition of MNCs has been given. Thereafter, some of the positive impacts as well as negative impacts of MNCs’ operation particularly in developing countries have been examined. Accordingly, three case studies are presented that make evident the positive, negative, and mixed impacts of multinational corporations on developing countries.