Post, known for its breakfast cereals, agreed to buy Golden Foods from affiliates of private equity firm Tricor Pacific Capital Inc and other shareholders for C$320 million ($301 million).
Golden Boy makes private label peanut butter and other nut butters. It also sells dried fruit, baking and snacking nuts.
Post said it will also buy privately held Dymatize from affiliates of TA Associates for $380 million.
Dymatize manufactures protein powders, bars and nutritional supplements under the Dymatize and Supreme Protein brands.
Post is strengthening its nutritional products brands, a market it believes will grow at a compound annual growth rate of 7 percent between 2014 and 2017.
It bought Premier Nutrition Corp in August and the Natural Cereal, Granola and Snacks Business of Hearthside Food Solutions in May.
Golden Boy had net sales of C$164 million and adjusted earnings before interest, taxes, depreciation and amortization (EBITDA) of C$23 million, for the nine months ended September 30, 2013, Post Holdings said in a statement.
Dymatize had net sales of $146 million and adjusted EBITDA of $23 million, for the nine months ended September 30, 2013, Post Holdings said.
St. Louis, Missouri-based Post said it will fund both the acquisitions with cash on hand and available debt borrowings.
