This study explores sources related to the Toba Batak vernacular architecture, particularly the concept of an ecological site plan for housing sourced from its indigenous knowledge. By analyzing numerous pieces of literature and Sait Nihuta as a specific site, this study describes an ecological site plan derived from the Toba Batak architecture which focuses on two main aspects: site planning, building form and orientation. Considering these unique aspects, the site planning tradition in a form that follows the characteristics of vernacular architecture can be applied as a basis for infilling design solutions of the most common types of site plan occurring in Toba urban areas. Using a qualitative approach, this study provides an in-depth knowledge of the ecological site plan through stages of description, elemental analysis; function, space and form, and interpretation of all three simultaneously. The intrinsic value of this observation is to define the process of adjustment of Toba Batak vernacular dwelling as an ecological site plan model for the purpose of infilling urban development in Toba Regency.