The "definitive agreement" to acquire the company was announced Tuesday; the deal is expected to close in the third quarter.
As part of the deal, Heritage Financial Corp. will pay $44.2 million for the company, half of it in cash and half in Heritage common stock. The combined company will have about $1.6 billion in assets.
"We are excited about this acquisition because it is another step towards fulfilling our growth initiatives and leveraging our strong capital position," Heritage President and Chief Executive Brian Vance said in a statement. "Valley Bank has created a great franchise that is well respected in the community."
Valley Chief Executive David Brown has been nominated to serve on Heritage's board. He also will assist with the transition, with plans to retire after a "successful integration."
Valley Community Bancshares had $242 million in assets at the end of 2012. Valley Bank was established in 1972 and serves customers throughout Pierce and south King County. It has nine bank branches.
This is Heritage's fourth bank acquisition since 2010, beginning with Cowlitz Bank in the Longview area, followed by Pierce Commercial Bank of Tacoma, Northwest Commercial Bank of Lakewood and now Valley Bank.
For more on this story, see Wednesday's Olympian.