Measurements of the dynamic surface elasticity and surface pressure of solutions of green fluorescent protein (GFP) indicate the formation of a dense protein monolayer with a relatively high surface elasticity of approximately 65 mN/m, and are typical for solutions of globular proteins. The mixed solutions of GFP and poly(N,N-diallyl-N-hexyl-N-methylammonium chloride) (PDAHMAC) demonstrate more complex behavior. During the first adsorption step the surface properties are determined by an unbound component, while the next step is mainly the adsorption of the complexes. The dynamic surface elasticity at relatively low polyelectrolyte concentrations (< 2*10⁻⁴ g/l) is close to the values for pure protein solutions when the surface pressure is less than 15 mN/m. At higher surface pressures the adsorption of complexes results in an increase of the surface elasticity up to 80 mN/m. If PDAHMAC concentrations are higher than 2*10⁻⁴ g/l, the kinetic dependences of the dynamic surface elasticity become non-monotonic and this quantity does not exceed 45 mN/m. The local maximum of the surface elasticity is a result of the formation of the distal region of the surface layer by the polyelectrolyte. Beyond the subsequent local minimum the surface elasticity starts to increase again due to the adsorption of GFP/ PDAHMAC complexes.