The PlayStation Vita sold 321,407 units in its first two days on sale in Japan, according to research firm Enterbrain.
The data, reported by Andriasang, covers December 17 and 18 and puts the Vita behind the Nintendo 3DS, which sold 371,326 in its first two days.
The number of Vita units sold is almost half the rumoured initial shipment of 700,000.
The Vita's predecessor, the PSP, sold 166,074 units in its first day - second day sales are not available.
The PlayStation Vita launches in Europe and the US in February. The European launch line-up includes Uncharted: Golden Abyss, Motorstorm RC, ModNation Racers: Road Trip and WipEout 2048.
To read Rob Fahey's latest editorial, in which he considers the Vita as one of the key launches of 2011, click here.