We analyze endogenous choice of organizational forms between U-form and M-form in the multiproduct mixed duopoly. With managerial delegation in public and private firms, we find that choosing M-form for the public and private firms is a dominant strategy under mixed duopoly in either Bertrand or Cournot competition. This is in contrast with the result obtained under privatization. In equilibrium, social welfare and consumer surplus with M-form under mixed duopoly are greater than those with U-form under privatization.