FORTUNE — The Hillshire Brands Co. HSH has agreed to pay about $6.6 billion, including debt, to acquire packaged foods company Pinnacle Foods Inc. PF , a deal that is expected to add to earnings and further diversify Hillshire’s portfolio.

The deal would combine Hillshire’s portfolio, which includes Jimmy Dean sausages, Ball Park, and Hillshire Farm, with Pinnacle’s Wish-Bone condiments, Mrs. Butterworth’s syrups, and Celeste pizzas.

Hillshire Brands chief executive Sean Connolly said the acquisition would strengthen the combined companies’ position in the frozen foods and refrigerated aisles, as well as in the center of the store.

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The sale would end private equity firm Blackstone Group LP’s BX control of Pinnacle Foods. Blackstone acquired Pinnacle Foods in 2007, and in 2013 it launched an initial public offering for the company, but still owned about 51% of Pinnacle Foods’ common stock.

Pinnacle Foods itself has grown through acquisitions, buying Birds Eye in late 2009 and Wish-Bone last October. The company had annual net sales of $2.5 billion in fiscal 2013 and says its products can be found in over 85% of U.S. households.

Under the terms of the agreement, announced Monday, each share of Pinnacle Foods common stock will be exchanged for $18 in cash and 0.50 shares of Hillshire Brands stock.

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The implied purchase price, based on the 10-day average closing price of Hillshire Brands as of May 9, is $36.02 per share — an 18% premium to Pinnacle Foods’ closing price on Friday. At that valuation, the deal excluding debt is worth $4.22 billion.

The transaction, which won approval from both boards of directors, is expected to close by September.

The combined company will use the Hillshire Brands name and will be based in Chicago.