In an unexpected decision, the BOJ eased monetary policy on worries that lower oil prices would affect consumer prices.
The central bank will increase the pace at which it expands base money to 80 trillion yen ($726bn; Â£454bn) a year, instead of 60-70 trillion yen.
The benchmark Nikkei 225 index closed up 4.8% at 16,413.76 after the news.
It had hit a seven-year high of 16,455.84 in mid-afternoon trade after rising by more than 5%. The dollar rose 1.2% to 110.68 yen, the highest since January 2008.
Several pieces of data out of Japan in the morning showing a weaker economy also failed to dent investor sentiment.
The country's annual core consumer inflation eased for a second straight month in September, while its jobless rate rose in the same period. Household spending also fell more than expected last month, adding to evidence that the central bank would probably maintain its massive stimulus programme.
Asian shares, meanwhile, were already up after positive economic data from the US showed strength in the world's largest economy.
Data showed the US economy grew at an annual rate of 3.5% in the third quarter. The news came a day after the Federal Reserve announced the end of its monetary stimulus programme.
Greater China shares followed the uptrend, with Hong Kong's Hang Seng index closing up 1.25% at 23,998.06 points.
On the mainland, the Shanghai Composite closed up 1.3% at 2,420.9 points.
In Australia, the benchmark S&P/ASX 200 closed up 0.9% at 5,526.60 points, following Wall Street's gains overnight.
Shares in heavyweight miners BHP Billiton and Rio Tinto rose 0.8% and 1.8% respectively.
In South Korea, the Kospi was up 0.3% at 1,964.43 points.

The 6ft 4ins midfielder was recommended to the club by former Walsall and Bermuda striker Kyle Lightbourne.
The 18-year-old has been training with the League One Saddlers since appearing in a development squad match in April.
"I've loved it here, the way the club has treated me," he said. "And how the players have welcomed me straight in."
Butterfield will initially work under the vastly experienced John Ward, Walsall's professional development coach.
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Nancy McAdam has been presented with a British Empire Medal after earlier in the year being named in the Queen's Birthday Honours list.
Ms McAdam, who lives on a croft on the Black Isle, is a longstanding member of the Scottish Dementia Working Group.
With others she founded Highland Dementia Working Group and Inverness Dementia Memory Group.
She was presented with her honour by Janet Bowen, Lord Lieutenant of Ross and Cromarty, incorporating Skye and Lochalsh.
Ms McAdam said: "I am simply thrilled. It is a great honour to get a British Empire Medal."
Ms Bowen said: "I was delighted to be able to present Nancy with her medal in recognition of the impact she has had on her community.
"I have learned so much from Nancy, particularly how it is possible to live well with dementia.
"I greatly admire how she came to terms with her diagnosis. Nancy is a wonderful example to us all."
Japan led Asian shares higher after the Bank of Japan (BOJ) surprised markets by announcing more stimulus measures.
[NEXT_CONCEPT]
Walsall have completed the signing of Bermudian teenager Kacy Milan Butterfield on a one-year deal, subject to receiving international clearance.
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A woman has been recognised for her work with charities helping people with dementia.