This study seeks to assess the maintenance and promotion of professional ethics in the public procurement systems of Zimbabwe from 2009 to 2013. The information gathered reveal causal factors behind the violation of professional ethics. The Public Choice Theory propounded by Buchanan and the Principal-Agent Theory will help in explaining why such results have been attained. This paper was compiled after reviewing some procurement publications, journal articles, and newspapers as well as employing questionnaires and interviews. The research found that there is rampant and endemic violation of professional ethics in the Zimbabwean public procurement systems since the 1990s. About US$2 billion is believed to be lost due to financial indiscipline in 2012 only. This was because of a multiplicity of factors which acted as contributing factors for the thriving of corruption. Among these several factors include political predation, low remuneration levels as well as lack of knowledge which goes with the rigors of public procurement business. The study concludes that the determinants of unofficial practices are mainly due to political predation thereby impacting negatively on the economy. The study also makes some recommendations on how professional ethics could be fully maintained and promoted and such recommendations include decentralizing public procurement, national commitment towards rooting and stamping out graft, training of procurement officials, adopting e-commerce mechanisms and ensuring compliance to the code of conduct. The paper also notes the effects of financial indiscipline in the State Procurement Board. Zimbabwe’s public procurement systems if managed properly, would reduce skewed and uneven development, lure foreign investors and improve service discharge in the form of quality project implementation in the public sector.