After the close on Thursday, the video game retailer reported third quarter adjusted earnings of $0.57, missing expectations for $0.60.
Revenue came in at $2.09 billion, missing expectations for $2.2 billion. Comparable stores sales fell 2.3% in the third quarter.
Following the results, shares were down as much as 12%.
In a statement, GameStop CEO Paul Raines said: "Overall, most of our major product categories performed very well, but our third quarter results were impacted by Assassin's Creed Unity moving out of October."
The company said the Assassin's Creed delay affected both top- and bottom-line results in the third quarter.
GameStop's guidance for the fourth quarter also disappointed, with the company saying it now sees comparable store sales coming in between -5% and +2%.
The company expects profit in the fourth quarter to come in between $2.08-$2.24 per share, below the $2.28 expected by the Street.
GameStop also expects to miss current profit forecasts for the full year, with the company saying earnings in fiscal 2014 will total $3.40-$3.55 per share, below the $3.68 currently expected by Wall Street.
Here's the full release from GameStop.