Shares jumped and the Japanese Yen fell against the USD as the Bank of Japan decided to further ease monetary policy in a bid to boost the economy.
The Nikkei 225 index was stronger by 4.8% to 16,409.50 on local buying.
The USD/JPY was trading up 1.5% at 110.86.
The central bank will expand its asset purchase program, the Japan news agency Kyodo reported.
It will buy Japanese government bonds from financial institutions so that their amount outstanding will increase at an annual pace of about 80 trillion yen, up about 30 trillion yen.
The BOJ Policy Board showed a split in making the decision, with four of its nine members opposing the additional easing. Governor Haruhiko Kuroda and his two deputies voted for the decision.