Harper finished with 21 points, leading five Auburn players in double figures and helping coach Bruce Pearl's Tigers (18-2, 6-1 SEC) take over sole possession of first place in the conference.
Desean Murray and Bryce Brown each finished with 16 points, and Mustapha Heron added 14 points and 12 rebounds for Auburn, which is off to its best start since the 1998-99 season.
Kassius Robertson scored 21 points and Jordan Barnett finished with 19 points to lead Missouri (13-7, 3-4), which hurt itself with 21 turnovers and continued its up-and-down campaign in coach Cuonzo Martin's first season in Columbia.
Harper poured it on in the second half, draining back-to-back 3-pointers that extended Auburn's lead to 70-54 with eight minutes to play. Harper hit five of Auburn's 14 3-pointers.
The game was tight in the first half. Anfernee McLemore hit a 3-pointer that gave Auburn an early 10-9 lead. Auburn would lead the rest of the way and took a 41-36 edge into halftime behind 13 points from Murray.
Barnett had 14 points in the first half.
Robertson knocked down a 3-pointer to cap an 8-0 run for Missouri early in the second half. Auburn always had the answer, though, and moved into first place in the SEC with Florida's loss to South Carolina.
Jordan Geist finished with 12 points for Missouri, and Kevin Puryear came off the bench to add 10 points.
Auburn ran off 14 consecutive wins before falling at Alabama last week. Auburn has now bounced back from that loss with two straight SEC wins, and it returns home to host LSU on Saturday.
Missouri has lost three of four and is facing a stretch of two straight SEC road games, beginning Saturday at Mississippi State.
--Field Level Media
Auburn | Missouri | |
Jared Harper 21 | Scoring | Kassius Robertson 21 |
Jared Harper 6 | Assists | Terrence Phillips 3 |
Mustapha Heron 11 | Rebounds | Jontay Porter 8 |
Bryce Brown 7 | Free Throws Made | Kevin Puryear 6 |
Jared Harper 3 | Steals | Jontay Porter 2 |
Anfernee McLemore 6 | Blocks | Reed Nikko 2 |