Abstract Guided wave scattering by an arbitrarily shaped elastic inclusion in a flat plate is analyzed by using the three-dimensional elasticity. An inclusion is decomposed into a number of small subscatterers and the field scattered by the subscatterers is solved by using a multiple scattering theory. The transition matrix relating the scattering field by a single subscatterer and an incident field is utilized for the multiple scattering analysis, but near-field interactions among subscatterers must be considered because of the closely packed arrangement of subscatterers. This calls for an analysis of nonpropagating wave modes and requires consideration of their influences on near-field interactions. Most earlier guided wave scattering analyses were based on an approximate plate theory and the wavefunction expansion techniques based on the three-dimensional elasticity were developed only for a cavity with a small range of shapes and sizes. Therefore, this investigation presents new results applicable for wave scattering by an elastic inclusion with a wide range of shapes and sizes in a plate. Several numerical tests were conducted to ensure stable solution convergence; the scattered wave fields generated by using the developed method for some case studies were compared with those of finite element analysis.