Given a unital C * -algebra A, we prove the existence of the coproduct of two faithful operator A-systems. We show that we can either consider it as a subsystem of an amalgamated free product of C * -algebras, or as a quotient by an operator system kernel. We introduce a universal C * -algebra for operator A-systems and prove that in the case of the coproduct of two operator A-systems, it is isomorphic to the amalgamated over A, free product of their respective universal C * -algebras. Also, under the assumptions of hyperrigidity for operator systems, we can identify the C * -envelope of the coproduct with the amalgamated free product of the C * -envelopes. We consider graph operator systems as examples of operator A-systems and prove that there exist graph operator systems whose coproduct is not a graph operator system, it is however a dual operator A-system. More generally, the coproduct of dual operator A-systems is always a dual operator A-system. We show that the coproducts behave well with respect to inductive limits of operator systems.