In situobservations of fracture processes, combined with one to one related observations of fracture surfaces and finite element method (FEM) calculations, are carried out on notched tensile specimens of TiAl alloys for near fully-lamellar microstructure. The results reveal that most cracks are initiated and propagated at the interfaces between lamellae before plastic deformation. The driving force for fracture process is the tensile stress. In specimens with a slit notch, most cracks are initiated directly from the notch root and extend along lamellar interfaces. The main crack and a new crack are then linked by the translamellar cleavage fracture of the barrier grain with the increasing applied load. FEM calculations reveal that the strength along lamellar interfaces (interlamellar fracture) is as low as 50 MPa , appreciably lower than the strength perpendicular to the lamellae (translamellar fracture), which shows a value higher than 120 MPa.