The main aim of this study is to investigate why national trade union membership has declined in the period 1994 to 2014 in Malawi despite the provision of collective labour rights in the Malawi Labour laws. In particular, the study finds out the factors that contributed to the drastic drop in trade union membership over the period in question. The study period is from January, 2015 through November, 2015. The population of this study is 2045 while sample size is 144. The study involves six trade sectoral wide trade unions drawn from the Private, Parastatal and Government. Data has been collected using questionnaires, interviews and review of documents. The analysis of has been done using Nvivo and content analysis. The study finds that factors such as application of labour problems solutions to nonmembers; lack of trust on union leadership; end of employment relationship; the burden of paying membership fees; lack of knowledge of the benefits of membership; threats from employers; pro-employee legal framework and transparency by management are causes of trade union membership decline. The findings in this study are of great significance in the sense that stakeholders will be able to revitalize trade union membership by addressing the causes of decline.