Packaging Corp.'s offer of $12.55 per share represents a premium of 26 percent to Boise's Friday close.
Boise shares were trading at $12.53 before the bell. Packaging Corp. shares jumped 10 percent to $60.03.
(Read more: M&A setto surge following Vodafone's bumper deal)
Packaging Corp., the fourth-largest maker of containerboard and corrugated packaging products in the United States, said it would assume Boise's $714 million debt.
The deal, expected to add to earnings immediately, will increase Packaging Corp's containerboard capacity by 42 percent to 3.7 million tonnes (1 tonne = 1.102 metric tons).
The company also said the acquisition will boost its presence in the Pacific Northwest.
Packaging Corp was advised by Bank of America/Merrill Lynch while JPMorgan Securities advised Boise.
Including debt, the deal is valued at about $2 billion.