Labor-managed Cournot oligopoly with or without product differentiation is analyzed. First, the existence of Cournot equilibrium which is not necessarily unique is proved under general conditions based on the Brouwer fixed point theorem, which does not provide a direct computer method for finding the equilibrium. Second, a constructive proof of finding the unique equilibrium is presented for Cournot labor-managed oligopoly without product differentiation. [JEL Classification: L13, P13]