STAMFORD, Conn.—In his latest attempt to save jobs and keep businesses in Connecticut, Gov. Dannel Malloy on Tuesday announced $20 million of incentives to keep UBS AG's flagship trading floor and other operations in this city.

The announcement, which requires UBS to maintain a minimum of 2,000 employees in Stamford for five years, removed the uncertainty that emerged this summer as the firm moved traders and toured office space in New York City.

But...