The major objective of this study is to answer the question: to what extent is firmlevel performance measured by investment, productivity and export influenced by government measures aiming to stimulate competition and protect consumers against monopoly? To analyse this influence, the study assesses the effect of control of dominant firms through institutions, the effect of mergers to prevent industries becoming monopolized and the effect of control of anti-competitive behaviour. The analysis focuses on assessing firm-level effects due to existing government efforts to regulate business activity in order to ensure that it operates in the public interest. In particular, the study analyses the role of competition policy in influencing productivity, investment and export performance of Tanzanian manufacturing enterprises. The study focuses on the hypothesis that fair competition has a causal impact on the quality and quantity of manufactured exports, productivity and investment.