The deal also includes the assignment of a portfolio of client loans worth approximately $300 million, and is scheduled to be completed later this year, subject to regulatory approval.
Minneapolis-based Piper Jaffray currently employs over 800 financial advisors in almost 90 branches across the Midwest and western US, with total client assets of $52 billion.
The business will be incorporated into UBS's wealth management unit, operating in the US.
Commenting on the new acquisition, Marten Hoekstra, head of UBS Wealth Management US, said that it was good news for both the company and clients.
"This transaction is a natural fit with our current wealth management offering in the US," he said.
"This network of talented individuals will allow UBS to serve a broader base of clients, and Piper Jaffray Financial Advisors and clients will gain access to one of the worldâs leading wealth management platforms with an unrivalled reputation in the marketplace."
Before this latest acquisition, UBS already had a significant share of the wealth management market in North America following is takeover of US broker Paine Webber in 2000.