As a graduate, he is eligible to play immediately.
Countess, a senior who started 30 games in his career at Michigan and was All-Big Ten honorable mention last year, is expected to compete for a starting job in Auburn's secondary, which was a sore spot for the Tigers last season. The 5-foot-10, 185-pound Maryland native had 24 tackles and three pass breakups last season.
Auburn, which gave up the third-most passing yards per game in the SEC last season, also will welcome in former Georgia defensive back Tray Matthews, who sat out last season per NCAA rules.
Countess is one of five Michigan players with eligibility remaining who has left the program since new coach Jim Harbaugh took over. Running back Justice Hayes, center Jack Miller, quarterback Russell Bellomy and tight end Keith Heitzman are the other four.