The figure is also up from January 2009, which saw sales of 309K units.
A September 2008 price cut that brought the entry-level Xbox 360's price to $199 spurred the sales momentum that reached a peak during the holidays.
Microsoft also confirmed that the February digital release of the Grand Theft Auto IV expansion, The Lost and Damned, set a first-day sales record for Xbox Live. The add-on sells for $20 exclusively on Xbox 360.
The Xbox 360 version of four games occupied the month's top 10 list: Street Fighter IV, Call of Duty: World at War, Fear 2 and Skate 2.
Halo Wars, which fell outside of NPD's February retail calendar with a March 3 release, has sold 1 million units worldwide.
The firm said that the Xbox 360 software tie ratio stands at 8.2 games per console on average.