The purpose of this study is to discuss different ways of implementing the "Food Security in a Climate  Perspective  strategy 2013-15" in  relation  to  support  to  private  sector  development and  public-private  partnership  (PPP)  as  regards  agriculture,  climate  change  and  food security in Ethiopia, Malawi, Mozambique, Tanzania and Zambia. We assess eleven different cases  of  private  sector  development  and  their relevance  to smallholder  investments  in agriculture.  An  important basis for this  study  is  the  voluntary Principles  for  Responsible Agricultural Investments (RAI) developed by the Committee on World Food  Security (CFS). These  guidelines  define  both  business  enterprises  and  smallholders  as possible private sector actors, and thereby included  in private  sector  development.  The  implications  of the CFS-RAI guidelines is  that  investment  in,  by  and  with  smallholders,  and  support  to  such investments,  are  seen as private  sector  development.  We assess three  different  approaches to supporting private sector developments: i) promote an enabling environment for private sector  development;  ii)  provision  of  public  goods  and  services;  and  iii)  direct  investment support. In all three approaches, the interests and needs of both business enterprises, such as  companies, and  smallholders  should  be recognized.  The  enabling  environment  should balance  the  needs  and  demands  of  both  smallholders  and  business  enterprises; the  public goods   and   services should address factors affecting   both   smallholders   and   business enterprises, and direct support could be provided to both   business enterprises and smallholders.