The fracture of micro-cantilever Al2O3 specimens containing single grain boundaries is quantified via in situ bending experiments performed in the transmission electron microscope. Our result suggest that grain boundary complexion plays a dominant role in determining the fracture response, while the dopant chemistry has a secondary effect for the same complexion type. Y2O3 doped Al2O3 containing containing sub-monolayer adsorbates is tougher than the undoped material, but it becomes embrittled when the complexions transition to more multilayer complexions., which is considered less ordered. SiO2 doped Al2O3 has smaller fracture resistance than undoped, since SiO2 promotes similar multilayer complexions at temperatures lower than the processing temperature. In general, grain boundaries exhibiting more ‘disordered’ complexions types, those with multilayer adsorbates, are embrittled relative to undoped Al2O3.