Slip deformation in compatible-type tricrystal models subjected to tensile load is investigated by using a continuum-mechanics-based crystal plasticity analysis technique. Accumulation of geometrically necessary dislocations (GNDs) and statistically stored dislocations (SSDs) are studied in detail. Mutual constraint of crystal grains through the grain boundary plane does not occur in the compatible-type tricrystals, however, results of the analysis show non-uniform deformation and high density of GNDs accumulated in the form of band in the crystal grains. The mechanism of non-uniform deformation and formation of GN dislocation structure corresponds to deformation bands in the compatible-type tricrystals is discussed from the viewpoint of the imaginary disclination-type displacement field around the grain boundary triple junction accompanying the multi-body interaction and mutual restraint of shape change of the crystal grain due to the slip deformation in the active slip systems.