The Kings announced the agreement Tuesday but did not disclose terms of the contract. May became a free agent when Charlotte declined to make him a one-year qualifying offer of $3.7 million last month.
May had appeared in only 82 of a possible 328 games since being picked 13th in the 2005 draft because of a lingering knee injury and conditioning problems.
"It's a great opportunity for him and us as well," Kings director of basketball operations Geoff Petrie said. "We look forward to this being a chance for him to combine his talent with his health and motivation."
May's best season came in 2006-07, when he averaged 11.9 points and 6.7 rebounds. He played only 35 games that season because of knee pain that led to surgery. May missed all the 2007-08 season recovering from the operation.
May acknowledged he became depressed when he wasn't playing, and his weight soared to more than 300 pounds. He dropped some weight before the start of training camp last fall but struggled badly after starting the season opener. He soon fell out of favor with coach Larry Brown and was placed on the inactive list for long stretches.
May appeared in only 24 games, averaging 3.9 points and 2.9 rebounds. After the season he was confident he'd eventually show his potential. May worked out for teams earlier this month in Las Vegas and impressed Sacramento enough to get another chance.
The Kings were an NBA-worst 17-65 last season, finishing with the worst record in franchise history. Sacramento also traded away a large chunk of its best players during the season, including former All-Star center Brad Miller, to clear space for the rebuilding process.
Paul Westphal was hired last month as the team's fourth head coach in just over three years. The Kings had two first-round picks in last month's draft, selecting guard Tyreke Evans fourth overall and forward Omri Casspi 23rd.
May, the son of former NBA player Scott May, led North Carolina to the 2005 national championship. He was named the Most Outstanding Player of the tournament.