A Securities and Exchange Commission filing didn't say why Metropoulos was selling the shares.
The Kansas City, Mo., company, whose namesake cupcakes just turned 100 years old, isn't issuing shares in the offering and won't receive any proceeds.
After the offering, 120.9 million Class A shares will remain outstanding. The shares of Hostess Brands closed down 4.9% at $13.66.
Morgan Stanley is running the books for the deal. The firm will offer the shares periodically on the open market and through private transactions at prices tied to the market or negotiated.
For the first half, Hostess earned 31 cents a share compared with 41 cents in the year-earlier period. Sales rose 9.2% to $463.8 million.