Room temperature Au-to-Au bonding has shown a promising potential for microelectromechanical systems (MEMS) encapsulation. However, the long-term reliability remains one of the critical concerns for the integration of this bonding technology in MEMS wafer-level fabrication. We have demonstrated the hermeticity and reliability of room temperature Au-to-Au bonding of thin seal-rings as narrow as 40 µm. Hermiticity was demonstrated over more than one-year at ambient conditions, corresponding to a leak rate below 10 -12 Pa.m 3 s -1 . Also, accelerated hermeticity testing in an elevated temperature and humid environment has shown excellent reliability for the first time. This type of bonding appears to be a suitable method for MEMS wafer-level packaging that requires low temperatures and/or operation in harsh environments.