We　develop　and　examine　a　framework　for　the　knowledge　spillover　theory　of　entrepreneurship　in　alliances.　Our　framework　regards　entrepreneurial　opportunity　as　endogenous,　and　entrepreneurial　firms　as　heterogeneous.　The　empirical　findings　show　that　partners＇　knowledge　protection,　which　is　regarded　as　a　knowledge　filter,　can　increase　knowledge　spillovers　in　an　alliance.　Moreover,　this　relationship　is　contingent　on　the　strength　of　a　focal　firm＇s　entrepreneurial　orientation　and　on　alliance　type　(equity　joint　venture　versus　nonequity　joint　venture).　Results　also　reveal　that　knowledge　spillovers　in　an　alliance　enhance　alliance　performance　more　significantly　than　they　enhance　firm　performance.