Photon upconversion has received substantial attention owing to its great promise in broad applications from bioimaging to other frontier fields like display, upconversion laser, information security and anti-counterfeiting. A smart control and manipulation of the upconversion luminescence has always been a key topic, however, to date the most efficient mechanism for upconversion nanoparticles remains the energy transfer upconversion and recently reported energy migration mediated upconversion. Recently, we found that the interfacial energy transfer (IET) is also an efficient approach for enabling and tuning photon upconversion of lanthanide ions. Moreover, it can be used for the mechanistic understanding of the interionic interactions such as energy transfer and energy migration on the nanoscale. In this review, the recent advances of the research on the IET are summarized, the principles for designing IET process and typical examples are discussed together with its applications in both mechanistic research and frontier information security. The challenges and perspectives for future research are also commented.