This article intends to conceptualize the problem of low interagency collaboration in implementing local social welfare policies into a system dynamics model. This conceptualized model is introduced to explore the possible factors facilitating and hindering interagency collaboration between Department of Social Welfare (DSW) of city government and Social Affairs Section (SAS) of district office in both Taipei City and Kaohsiung City of Taiwan. The model combines insights from policy implementation theory, qualitative data from interviews with DSW and SAS staffs, and system dynamics literatures. Although this model is not yet formulated, several insights have been obtained. This study finds that the institutional design has made cooperation between two agencies difficult. Such an interagency relationship is reluctant compliance rather than partnership. This article argues that a homogeneous realization of the cooperation pattern among implementation participants is necessary for building effective interagency relationships in policy implementation.