The broad objectives of the study was to establish the moderating effects of firm characteristics, competitive environment and strategy implementation on the relationship that exists between strategic planning and performance of Kenyan State Corporations. Specific objectives of the study were to determine the individual and joint moderating effects of firm characteristics, competitive environment, and strategy implementation on the relationship between strategic planning and performance of state corporations in Kenya. The study was oriented by the positivist view which uses surveys to verify hypotheses, statistical analyses and quantitative statistics. The targeted population of interest in this study was all state corporations in Kenya (commercial corporations and commercial corporations with strategic functions).