The 6-foot-11 Moultrie was the 27th overall pick in the June 28 NBA Draft by Miami, but was traded to Philadelphia later in the evening.
The 76ers invested their 15th overall pick on 6-foot-8 St. John's forward Maurice Harkless, a 19-year-old who was the Big East Rookie of the Year. Harkless, who averaged 15.5 points and 8.6 rebounds in his only college season, also signed on Tuesday.
Philadelphia ranked only 19th in rebounding margin last season and was looking to bulk up inside. "Both of those guys are very, very good rebounders," said 76ers head coach Doug Collins. "We were thrilled to get them both."
The terms of the three-year deals were not made public, but the Philadelphia Inquirer reported that Harkless will make $1.73 million next season while Moultrie will make $1.04 million.
Collins said that Harkless was the team's No. 1 draft priority. "And if he had not been there at No. 15, we were going to take Arnett," Collins said. "To get Arnett at No. 27, we were thrilled."
Moultrie, 21, spent one season in Starkville after transferring from UTEP. He averaged 16.4 points and led the SEC in rebounding at 10.5 per game. He was a first-team All-SEC selection.
"We worked out six guys in one day here, and Arnett - in five minutes - separated himself from all five of those other guys while I was watching him work out," Collins said.
Moultrie, who played high school basketball in Memphis, was introduced by the Sixers after the draft with the No. 1 jersey but will wear the No. 23 he wore in college. "I'm looking forward to competing every night," he said.