Like-for-like sales in the five weeks to January 5 climbed 5% - with online sales "ahead of expectations", rising 39% over 18 weeks to the same date.
The department store said figures were boosted by its seasonal advertising campaign, product range and online sales.
Web sales accounted for 12.6% of total sales over the 18 week period, compared to 9.3% in the previous financial year.
As a result, it said the higher than anticipated online sales would have an impact on its warehousing and distribution costs over the course of the year, which are expected to increase from 3.2% to 3.5% as a percentage of sales.
The retailer also admitted it cut its prices ahead of Christmas because of greater promotional activity on the wider high street - a decision that hit its margins more than it had previously forecast.
Michael Sharp, chief executive, said: "I am pleased with our performance in the first four months of our financial year.
"The trading environment was extremely challenging but we focused on meeting the needs of our customers and executing the four pillars of our strategy.
"I would like to thank the whole of the Debenhams team for their tremendous efforts in delivering this performance.
"We continue to believe that whilst customers have become acclimatised to the new economic reality, we don't anticipate a significant change in consumer confidence in the remainder of the year.
"We remain committed to prudent investment in key areas of the business to deliver long-term substantial growth as well as driving shareholder value."
Debenhams is not the only retailer to buck the gloomy retail trend.
On Monday, House of Fraser posted record trading results for the festive period, with like-for-like sales up 6.3% in the six weeks to January 5.
Last week, John Lewis revealed it made £684.8m in the five weeks to December 29 - up almost 15% on the same period in 2011.
All three retails giants - among the first to provide Christmas trading updates - have all reported a surge in online sales.
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