In this article, branched NaYF4 nanocrystals have been successfully synthesized via a simple hydrothermal method. On the basis of the analysis of HRTEM and TEM images, the growth modes of the branched structure and further branching behavior have been proposed. The up-and down-conversion luminescence of branched NaYF4:Er3+/Yb3+ and NaYF4:Eu3+ have been characterized. Multiarmed NaYF4 phosphors can be introduced into polystyrene to form composite luminescent polymers because of its special geometrical shape. In conclusion, the luminescent branched particles should be of wide potential application as building blocks in the future nanoscience and nanotechnology.