Joasaphus took monastic vows in Solovetsky Monastery. In 1621, he became a hegumen at Pskovo-Pechorsky Monastery. In January of 1627, Joasaphus was appointed archbishop of Pskov and Velikiye Luki. He is known for his protection of Pskov's trade privileges and resistance to pretensions of the German merchants, for which he would be punished by the patriarch. Upon Philaret's death in 1634, Joasaphus was appointed his successor. Joasaphus I is buried in the Cathedral of the Dormition in the Moscow Kremlin.