Basing on National Export Strategy elaborated in 2011 and aligned with EDPRS and vision 2020, the export of products and services could be increased to 11.5% in 2020. However few companies are committed to comply with the requirements of Quality Management System which are helpful for market access. Few companies which are ISO certified have gained acknowledgement and credibility of their products and services at the international level. So far, in Rwanda, there was no study done on the role played by certification to ISO standards in the business success. It is therefore, this study aimed to assess the contribution of ISO 9001:2008 certification to the market competitiveness of manufacturing companies in Rwanda. The methodologies employed Spearman Correlation coefficient and student t-test.The findings report a significant difference between sales revenue, Return on Investment (ROI), and market share for the period before and after certification (in favor of after certification). Findings also report a positive and significant relationship between certification to ISO 9001:2008 and market competitiveness.