A female harbor seal pup rescued along the coast of San Diego on 13 June 2012 was diagnosed with bilateral mature cataracts, apparently congenital, in association with vitreal herniation in the anterior chamber of each eye. The cataracts were surgically removed on 1 August 2012 with single-port aphakic phacoemulsification and automated anterior vitrectomy. Postoperative monitoring during the next several weeks indicated that vision had been functionally repaired and that she could visually orient to and capture live fish in three different environments and in the presence of other animals. Consequently, we equipped the seal with a satellite-linked radio transmitter and returned her to the Pacific Ocean on 21 November 2012, and then monitored her movements until radio contact ended on 2 March 2013. She remained along the San Diego coast from 21 November until 5 December 2012 when she relocated to the Coronado Islands and remained there until 26 December. She then traveled directly to San Clemente Island and remained foraging in the near-shore kelp beds there through 2 March 2013, when radio contact ended. To our knowledge, this is the first published report of cataract treatment in a marine mammal using high-frequency ultrasound to emulsify the lenses followed by suction removal of the emulsified microfragments (i.e., phacoemulsification). Moreover, the rapid postoperative recovery of the seal and its quick acclimation, orientation, navigation, and foraging in marine habitats after return to the Pacific Ocean indicates that these surgical procedures can be safe and effective treatments for cataracts in seals, with substantially reduced postsurgical complications relative to other types of lens fragmentation and removal procedures.