The article explores how privatization and regulation policies impact mixed markets where private and public firms compete. Partial privatization can improve welfare in quantity competition for substitute goods and in price competition for complementary goods. Full privatization is never optimal. Public firms can sometimes make more profit than private firms, especially in quantity competition. Taxing public and private firms equally is important, and price regulation is preferred over quantity regulation. Previous studies suggest that privatization can be beneficial in competitive markets, and having only one public firm can be optimal in the short run.