The purpose of this paper is to identify the roles of decentralization of the strategic decision-making process between contextual factors and decision process output. From analysis of alternative research approaches, a field survey was most appropriate methodological choice. This study is a field study of real organizations rather than an artificial setting. The questionnaire consists of items measuring the variables of primary interest, namely the independent, mediator, and dependent variables. The study was conducted in central part of the country involving medium and large size manufacturing firms. The results of hierarchical regression analysis indicate that decentralization in the strategic decision-making process mediates the influence of organizational slack, environmental dynamism and managers need for achievement on quality of the decision process output. But do not mediate the influence of the decision familiarity on quality of the decision process output. Key Words: Strategic decisions, Decision?s familiarity, Environmental dynamism, Organizational slack, Need for achievement.