There　are　two　typical　forms　of　trust　in　organisational　settings　institution-based　trust　and　interpersonal　trust.　The　role　of　interpersonal　trust　in　promoting　interdepartmental　knowledge　sharing　has　been　investigated.　The　effect　of　institution-based　trust,　especially　the　joint　effect　of　institution-based　and　interpersonal　trust,　on　interdepartmental　knowledge　sharing　has　not　been　adequately　described.　This　article　builds　a　conceptual　model　to　describe　the　independent　and　joint　effects　of　these　two　forms　of　trust　on　the　satisfaction　and　success　of　interdepartmental　knowledge　sharing.　The　moderating　role　of　knowledge　tacitness　is　also　described　in　this　model,　which　is　tested　on　294　collaborative　task　scenarios　between　departments　within　Chinese　IT　firms.　The　empirical　results　essentially　support　the　proposed　model　and　contribute　to　organisational　trust　and　interdepartmental　knowledge-sharing　discussions　by　clarifying　the　substantial　roles　of　these　two　forms　of　trust　in　the　context　of　interdepartmental　collaboration　and　knowledge　sharing.　Copyright　©　2016,　IGI　Global.