Sebastian recorded 96 career tackles in his career with the Golden Bears, starting six of 33 career games. He added two interceptions, two tackles for loss and one forced fumble.
"I'm very thankful to head coach Brian Kelly and the rest of the coaching staff and administration for giving me the opportunity to come play at the University of Notre Dame," Sebastian said in a release. "I think academically, spiritually and athletically will make Notre Dame a perfect fit. I've got one year to make an impact, and I plan on making the most of this opportunity. I look forward to joining the Notre Dame family."
Sebastian graduated from Cal in December with a degree in sociology and will enroll at Notre Dame in June. He will be immediately eligible to play in the 2015 season, and he could push for a starting spot, as the Irish are thin at safety.
The McDonough, Georgia, native was ESPN's No. 68 player from the class of 2011, and he is the second fifth-year player to transfer to Notre Dame in as many years. Defensive back Cody Riggs started for the Irish in 2014 after transferring from Florida.