Domain structures are examined on ribbon-shaped (111) platelets of NiO crystals containing thin lamellae twinned on the (111) plane with respect to each other. Together with configurations of T-domains realized across the twin planes detailed configurations of T-walls are determined by optical and X-ray observations. Characteristics of observed T-domain structures can be reasonably interpreted by considering the elastic interaction between T-walls and twin planes through the rhombohedral striction as well as the anisotropic shape of specimen.