During European morning trade, the EURO STOXX 50 climbed 0.47%, France’s CAC 40 advanced 0.46%, while Germany’s DAX 30 rose 0.28%.
The BoJ said earlier that it was boosting the size of its asset-purchase program by JPY10 trillion, in an effort to boost slowing economic activity and to counter the strengthening yen.
Meanwhile, investors remained cautious amid reports Spanish Prime Minister Mariano Rajoy remains uncertain about asking for help from the European Central Bank's new bond-purchasing program, which would mean signing up to a permanent bailout fund.
Markets were also jittery as the yield on Spain's 10-year government bonds was hovering at 5.89% earlier Wednesday, close to the 6% threshold, widely seen as unsustainable in the long term.
Financial stocks were sharply higher, as shares in German lenders Deutsche Bank and Commerzbank surged 1.60% and 2.02%, while France's Societe Generale and BNP Paribas climbed 0.58% and 0.53% respectively.
Peripheral lenders also added to gains, with shares in Italian banks Unicredit and Intesa Sanpaolo advancing 1.24% and 0.40%, while Spain's Banco Santander and BBVA rose 0.66% and 0.15%.
Elsewhere, Heineken soared 6.27% after stakeholders said they will back the company’s USD4.6 billion bid for Asia Pacific Breweries Ltd.
In London, commodity-heavy FTSE 100 added 0.21%, supported by sharp gains in oil and mining stocks.
Oil giant Anglo American was one of the session's top gainers, with shares jumping 2.18%, while rival group BP climbed 0.89%.
Also on the upside, mining giants BHP Billiton and Rio Tinto rallied 0.76% and 0.68%, while copper producers Xstrata and Kazakhmys advanced 0.59% and 3.54% respectively.
Lonmin also gained ground, soaring 4.29%, after the company reached a pay agreement with workers at its Marikana mine in South Africa.
Meanwhile, financial stocks were mixed. Shares in HSBC Holdings surged 1.24% and the Royal Bank of Scotland rose 0.49%, while Lloyds Banking and Barclays declined 0.15% and 0.29%.
In the U.S., equity markets pointed to a higher open. The Dow Jones Industrial Average futures pointed to a 0.26% rise, S&P 500 futures signaled a 0.29% increase, while the Nasdaq 100 futures indicated a 0.29% gain.
Later in the day, the U.S. was to publish official data on building permits and on housing starts, followed by government data on crude oil stockpiles, as well as an industry report on existing home sales.