This paper reports about how product diversification strategies drive for firm performance through managerial skills. Extant literature has presents that increases in product market diversification generate both positive and negative impact on firm performance. The paper aims to embed that diversification in many industries are highly imputable to the power to cross-sell their products, get cost savings, enter the new markets, produce hybrid products and increase brand image. Also with the global financial market liberalization, firms in many countries are increasingly using the product diversification strategies. This is to expand the market share of the firm and also to improve the financial performance. When investigating managerial skills it is more important to identify seven major factors of management tasks. This includes managing individual performance, instructing to their subordinates, planning and allocating the resources, coordinating of mutually beneficial groups, managing of their group performance, continually monitor the business environment and represent in one's staff. Also this is important to examine the findings has given clear-cut differences in the importance of the role of the level of the manager. Many studies have examined managerial skills in many ways. This is about predicting the effectiveness of managers from the managers' skills dimensions such as skills of technical, administrative, human and citizenship behavior. In some studies administration skills have a more effectiveness in managers' effectiveness. There are few empirical studies that describe managerial skills evaluations of firms. This is an organizational level as a moderator of the skill of managerial effectiveness relationship. Future researches need to continue to dig into new variables to identify skills and features that help managers to do more successful. Therefore this paper explains how managerial skills related to the product diversification strategies to drive to firm performances.