Sirtuin7 (SIRT7) is a NAD(+)-dependent protein deacetylase which belongs to sirtuin family. Although sirtuin proteins have attracted a great deal of attention, little is known about SIRT7. SIRT7 participates in rDNA transcription in the nucleolus. However, recent reports show that SIRT7 has additional novel functions. This review summarizes all findings about SIRT7, and highlights its critical roles in cellular functions.