The decision rules him out of Leinster's Amlin Challenge Cup quarter-final against Wasps in April and two games in the Rabodirect Pro12 league.
The centre was cited following the incident in Ireland's 22-15 defeat in Rome on Saturday and could have faced a ban of nine weeks. As it is, he is suspended until April 8.
O'Driscoll, 34, was sent to the sin-bin for only the second time in his 14-year professional career in the first half of the match at the Stadio Olimpico.
The act was out of character for O'Driscoll, who has a fine disciplinary record, and was evidence of his frustration as Ireland slumped to a first Six Nations defeat by Italy.
However, he was lucky to have escaped a red card for an incident that clouded what is thought to have been his 125th and final Test in a green shirt.
At Wednesday's hearing in front of an independent Six Nations Disciplinary Committee, the player admitted an act of foul play - but argued that it did not warrant a red card.
"After hearing from Brian O'Driscoll and his representatives, [the committee] allowed a reduction of two weeks of mitigation, particularly taking into account the player's exemplary previous playing and disciplinary record," a statement from the Six Nations said.
O'Driscoll has the right to appeal.
- Sports & Recreation