Six Bank of America Merrill Lynch
The defections show how serious a blow the loss of the veteran banker - one of the driving forces behind the breakup of Dutch lender ABN AMRO in 2007 - could be for Bank of America.
UBS Chief Executive Sergio Ermotti previously worked with Orcel at Merrill Lynch and appointed him for his famed contacts book, which should ensure a steady stream of deals.
Fluent in four European languages, Orcel, 48, is a 20-year Merrill Lynch veteran and the banker of choice for clients such as Spanish bank Santander
Even at the height of the financial crisis in 2008, Merrill Lynch paid him close to $34 million in stock and cash, showing his importance to the firm.
Orcel's reputation as a one-man deal machine may invigorate his new firm, but has also raised questions about his ability to coexist with Carsten Kengeter, the former Goldman Sachs
The most senior new hire is Javier Oficialdegui, who will become co-head of financial institutions for Europe, the Middle East and Africa (EMEA), alongside Edouard de Vitry, according to a memo obtained by Reuters.
Oficialdegui has 16 years' experience in the Iberian market, with a particular focus on bank deals, the memo said.
UBS and Bank of America declined comment.
Emilio Greco, who has 12 years' experience with Italian clients, will join the financial institutions group as a managing director alongside existing UBS bankers Diego Pignatelli and Annalisa Terracina, the memo said.
Alberto Palombi will join Guy Stevens in covering financial institution clients in EMEA emerging market countries, having had a similar role at Bank of America.
Javier Martinez-Piqueras will join to work in equity capital markets, the business that helps clients raise equity through rights issues and initial public offerings.
Two other hires were Christian Montaudo in Italy and Carles Guzman in Spain, a source familiar with the situation said.
(Writing by Douwe Miedema; Editing by Erica Billingham and David Holmes)