This paper presents an analytical model for the analysis of steel-concrete composite beams with partial shear interaction including the shear deformability of the steel component. This model is obtained by coupling an Euler-Bernoulli beam for the reinforced concrete slab to a Timoshenko beam for the steel beam. The composite action is provided by a continuous shear connection which enables relative longitudinal displacements to occur between the two components. The balance conditions are derived using the principle of virtual work and the numerical solution of the problem is obtained by means of the finite element method. Extensive numerical simulations are carried out on realistic three-span continuous composite beams to evaluate the effects of the shear deformability of the steel member on the overall structural response.