NTT DoCoMo Inc has established "a broad-based business tie-up" with China's largest mobile operator and the South Korean firm, the Japanese carrier said in a statement, as it searches for new business in Northeast Asia.
DoCoMo has been looking to expand abroad in search of growth overseas, away from Japan's saturated telecoms market.
A business cooperation committee to be set up by the three companies will consider further opportunities for collaboration.
The committee will look particularly at "dramatic changes occurring in the mobile market, including the further globalisation of corporate activities and the sharply rising popularity of smartphones," DoCoMo said.
Specific areas to be looked at also include international roaming, enterprise services and mobile network technologies.