Powered by fast-growing China and India, the Asia-Pacific region's millionaire ranks rose 10 percent to 3.3 million, second only to the 3.4 million residing in North America and inching ahead of Europe, which had 3.1 million.
Asia's combined wealth, up 12 percent to $10.8 trillion last year, surpassed Europe and threatens to overtake the United States and Canada, where wealth rose 9 percent to $11.6 trillion.
"Their capital markets may be emerging, but their economies have clearly arrived," John Thiel, head of Merrill's private banking group and its "Thundering Herd" of 15,700 U.S. brokers, told Reuters. "They're not 'emerging' anymore."
More than half of the world's millionaires are still found in the United States, Japan and Germany, but that the wealthy are spread among more countries, according to Merrill and global consulting firm Capgemini.
Assets held by millionaires worldwide rose by 9.7 percent to a record $42.7 trillion -- surpassing the previous high-water mark set in 2007 -- while the ranks of people with at least $1 million of investable assets, excluding their primary residence, rose 8.3 percent to 10.9 million, the report found.
Some of that growth came as manufacturing, exports and domestic growth helped places like Hong Kong, Singapore and India create legions of members for the millionaires' club.
The findings echo a PricewaterhouseCoopers report published Monday, which found that Singapore and Hong Kong could surpass London and Switzerland as the world's top wealth management hub by 2013.
Investable assets held by the very rich grew as stocks and other financial markets continued to climb from the depths of the 2008 financial crisis. Asia-Pacific millionaires, the survey found, were more heavily invested in local real estate.
Faith in equity markets is slowly returning, thanks to two strong years of gains since the panic of March 2009. Global equity holdings rose 4 percentage points last year to 33 percent of financial assets, back to the pre-crisis levels.
That said, the world's rich still placed a premium on liquidity, or how easily investments can be sold.
Thiel noted that investors in developed nations are still reacting to the fallout of the financial crisis, including Europe's sovereign debt crisis, the massive U.S. budget deficit and a real estate slump.
"Our clients are still a little risk-averse about increasing that exposure. There's still plenty of things to worry about domestically and internationally," Thiel said.
Investors' trust in wealth management firms also has recovered since 2008, when credit losses and market panic knocked out Bear Stearns and Lehman Brothers, and forced Merrill Lynch into a shotgun marriage with Bank of America Corp.
In 2008, half of the millionaires surveyed by Merrill and Capgemini said they were losing trust in their advisers and their banks. Confidence in firms has rebounded to 88 percent, though fewer than half of millionaires say they have much faith in regulators.
The ultra-rich -- people with more than $30 million to invest -- did even better than their regular-rich peers last year. Their ranks grew by 10 percent to 103,000, while their combined wealth rose 11.5 percent to roughly $15 trillion.
Merrill's report does not measure total wealth across all demographics, but indicates that the gap between the very wealthy and the rest of the world continues to widen.
Even among millionaires, wealth grew more concentrated: The super-rich represented fewer than 1 percent of millionaires, yet held more than a third of that elite group's wealth.
For the firms that make a living by managing their wealth, though, these are encouraging trends.
"Clearly it's a good environment to be in the wealth management industry," Thiel said. "We're hiring more people and expanding our advisory force."
