The Munster fly-half was cited for kicking out at Sean Cox during the 26-17 win over Edinburgh in last weekend's Heineken Cup clash.
It was feared that O'Gara could be hit with a four-week ban for the offence, but the European Rugby Cup disciplinary panel decided the player had acted "out of character".
An ERC statement read: "The independent Judicial Officer, Judge Jeff Blackett (England), heard evidence and submissions from O'Gara, who pleaded guilty to the offence.
"The Judicial Officer upheld the complaint and found that O'Gara had committed a petulant act which was out of character.
"He determined that the act was in the lower end of the IRB's sanctioning regime and taking into account the player's guilty plea and his good disciplinary record.
"Judge Blackett then determined that a two-week suspension would be wholly disproportionate to the level of offending as O'Gara had been body-checked by Sean Cox prior to the incident.
"He also accepted that O'Gara had intended to trip rather than to kick Cox. As there were no aggravating factors, he imposed a suspension of one week."
O'Gara will now sit out Munster's crucial Heineken Cup encounter against Pool 1 rivals Racing Metro at Thomond Park on Sunday.
Munster go into the game three points ahead of the French outfit, while Saracens are already assured of qualifying from the group.
And O'Gara will now be eligible for Ireland's Six Nations opener against Wales on 2 February.
Gilbert has released a new line of rugby cleats. The Gilbert Virtuo 8S is part of the exciting new product. Check it out.
The entire All Blacks apparel line has been updated for 2013/14. Check out the New Zealand All Blacks polo.
The Nike Tiempo is a solid rugby cleat and one of few styles still made from full-grain natural leather.
The Gilbert Blitz 8S rugby cleat is a great cleat at a great price of $69.99. Get a new pair of cleats today.
A cool looking all black rugby cleat with the high performance adidas is known for. Get in the Gear!
Wear the crest of the British and Irish Lions on your t-shirt. A great look for the summer.
$29.99
The All Blacks Performance t-shirt is black with hints of blue from the training jersey. Very Cool.
The New Zealand All Blacks training jersey for 2013/14. Get in the Gear!
The USA Rugby Pro Alternate rugby jersey is perfect for any fan of the Eagles. Get yours to wear during the summer Test matches.
The NEW All Blacks 2013/14 jersey has arrived at World Rugby Shop. Dare to wear the colors of the All Blacks.