Ms. Rothstein, a legacy Smith Barney adviser who joined Citigroup Global Markets Inc. in 1999, managed “approximately $2.5 billion” in assets, according to information released by Bank of America Merrill Lynch.
The firm didn't disclose her production levels with Morgan Stanley.
Ms. Rothstein wasn't available for comment.
So far this month, InvestmentNews has tracked eight moves by Morgan Stanley advisers to other firms. As a group, they managed $9.5 billion in assets.
Ms. Rothstein, who was No. 2 on the Barron's list of America's top 100 female advisers for the past three years, is also a perennial member of Barron's broader top-advisers list.
“If you were to ask Greg Fleming for a list of five advisers he didn't want to lose, she would have been on it,” said Danny Sarch, president of Leitner Sarch Consultants Ltd.
Mr. Fleming, a former president of Merrill Lynch, now holds that title at the Morgan Stanley unit.
Morgan Stanley spokeswoman Christine Jockle confirmed the departure of Ms. Rothstein but declined to comment further.
“This is a major loss for Morgan Stanley. She is one of the big names in brokerage in Los Angeles,” said Bill Willis, president of Willis Consulting Inc., a recruiting firm.
In August, Reuters reported that Ms. Rothstein was serving as a go-between for dozens of top-producing Morgan Stanley advisers and senior management. The advisers, frustrated with a new technology platform, reportedly were threatening to leave the firm.
Ms. Rothstein is taking 11 Morgan Stanley employees with her to Merrill's Century City office in Los Angeles. She will be reunited with Matthew Celenza and Larry DiGioia, two former adviser colleagues in the Beverly Hills office of Morgan Stanley, who spent a brief period with Barclays before joining Merrill in July.
They weren't on Ms. Rothstein's team at Morgan Stanley, according to Merrill spokesman Matthew Card, and will remain part of a separate team in the Merrill office.
Two other heavy hitters accounted for the bulk of the assets exiting Morgan Stanley this month. Jonathan Madrigano, a New York-based adviser managing $2 billion, joined JPMorgan Chase & Co., and Palmer Murray, an L.A.-based adviser managing $4 billion, according to Barron's 2011 rankings of top advisers, joined RIA firm Lourd Capital Management LLC.
Jason Lahita, an outside spokesman for Lourd, confirmed Mr. Murray's move.
But Morgan Stanley spokesman Jim Wiggins said that Mr. Murray left the firm for Lourd to become the trustee of a major family account and that his “two partners and a substantial portion of his managed assets” will remain with Morgan Stanley.
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