The player will be unavailable for South Africa's autumn internationals.
South Africa prop Wessels has been suspended of nine games for grabbing opponent Josh Murphy's private parts during the Blue Bulls' United Rugby Championship win over Connacht.
This event occurred in the 18th minute of the Bulls' 28-27 win in Galway on Friday, with opposing player Murphy being shown a 20-minute red card after responding aggressively by hitting Wessels on the head area.
After Murphy reported the incident to referee Mike Adamson, the situation was checked by the TMO, who found no conclusive video evidence.
The Bulls player remained on the field until he was replaced in the second half of the game.
Although the URC confirmed that Murphy's temporary sending-off was overturned by a governing body, the Springbok was found to have breached law 9.27, which specifies:
"A player must not engage in actions that is against the spirit of good sportsmanship. Such behavior covers grabbing, pulling or compressing the private areas."
The panel concluded that the incident met the level for dismissal and justified a three-month ban, the minimum ban under World Rugby regulations for such an infringement.
Nonetheless, Wessels' ban was reduced by three weeks because of his good conduct prior to and at the hearing and his good record.
The forward and the Pretoria-based team have the right to appeal, but as it stands, the suspension will prevent the 24-year-old out of the South African national team's autumn Tests against the Brave Blossoms, France, the Azzurri and Ireland.
He will additionally be absent for the his club's league matches against Glasgow, the Lions and the Cell C Sharks, as well as European cup fixtures with Bègles and Saints.
The prop has earned ten international appearances for the Springboks and was part of their tri-nations champion team over the summer.
The Connacht player, in contrast, is available to face the Irish rivals in Saturday's domestic clash after being exonerated.